Journal of Immunological Methods, 17 (1977) 63--72
63
© Elsevier/North-Holland Biomedical Press
T H E MOUSE CIRCUS: A SIMPLE APPARATUS FO R THORACIC DUCT
C A N N U L A T I O N AND CONTINUOUS I N TRA V E N O U S INFUSION
D.R. BAINBRIDGE
Department of Immunology, London Hospital Medical College, London, E1 2AD, U.K.
(Received 18 December 1976, accepted 18 March 1977)
A simple apparatus is described for maintaining mice during thoracic duct cannulation and/or continuous intravenous infusion, which involves much less restraint than current methods. An Appendix describes the techniques of intravenous cannulation which have been used for prolonged infusion or cardiac catheterisation.
INTRODUCTION Thoracic d u c t cannulation in rodents, first introduced for rats by Bollman et al. (1948) and successfully applied in mice by several workers (Shrewsbury, 1959; Gesner and Gowans, 1962; Boake and Woodruff, 1965; Sprent, 1973} continues to play an i m p o r t a n t part in investigating the role of l y m p h o c y t e s in i m m une responses. Current practice, however, involves severely restraining the animal's f r e e dom of m o v e m e n t ; given the sensitivity of l y m p h o c y t e s to stress steroids this m ay be unfavorable. The apparatus described here, a 'circus' rather than the cust om ary mouse 'wheel', was devised to keep the restraint on cannulated mice to a minimum; it is moreover mu ch simpler to construct. In principle it consists of a (perspex) platform bearing a central pillar made from a length of glass tubing in a r u b b er bung, which carries a freely rotating arm made from coiled wire. A wire harness is attached to the arm by a swivel clip and is taped to the mouse. This allows the animal considerable liberty to move in any direction e x c e p t a 180 ° twist. The thoracic duct cannula is threaded, out of the way, t h ro u g h the centre t ube to a collecting vessel underneat h the platform. Intravenous infusion during the first 24 h after cannulation, as r e c o m m e n d e d by Sprent (1973) for salt replacement, can be carried out using the mouse circus, if a mercury-sealed swivel j oi nt (Bainbridge and Wright, 1965) is e m p l o y e d in the infusion line. F o r sustained infusion the circus is more satisfactory than the tailtethering m e t h o d briefly described by Bainbridge and Wright (1965), at least when the latter is used with swivel joints available commercially. These have proved to require much greater t o r q u e than original examples o f the design, m o r e than mice can readily apply at the tip o f their tails.
64
The platforms can be conveniently placed on scaffolding constructed from Climpex Tubing (Baird and Tatlock, London, Ltd, P.O. Box 1, Romford, Essex RM1 1HA, U.K.). A circus assembly in current use in this laboratory consists of 3 tiers, each of 8 platforms set side by side, accommodating 24 mice at a time. The infusion lines are supplied by simple multichannel deltaperistaltic pumps (modified from Bainbridge and Wright (1965). Commercial variations on the design are sold as Watson--Marlow pumps, Fisons Scientific Apparatus Ltd., Loughborough, Leicestershire, U.K.), with individual or c o m m o n reservoirs as required. D E S C R I P T I O N O F THE A P P A R A T U S
Figures 1, 2 and 3 illustrating the construction of the apparatus and installation of the mouse are largely self-explanatory. The following comments are intended to amplify certain points.
Figure 1 a) Paper is wrapped around the platform and held in place by a small bung, which also serves to prevent the platform sliding a b o u t on the scaf-
D
........i....... ~i'~'~i'i'i~"!~'~l'~!
'~! ~'1¸~¸~¸~''~¸¸¸¸~ ...............
Fig. 1. C o n s t r u c t i o n o f a p p a r a t u s , a) D i m e n s i o n s o f t h e p l a t f o r m and pillar, b) Construct i o n o f t h e swivel and harness, c) A s s e m b l y o f swivel on the pillar.
65 folding. When dirty t he platform can be changed easily for a new one, if need be while the mouse is in place. b) T w e n t y - o n e SWG stainless steel wire is w o u n d around an iron bar of suitable diameter to make the coil. The slide at one end of the coil and the rings on the extension arm at the ot her are made using small round-tipped pliers and wire-snips. The slide enables the coil to rot at e freely back and forwards. The triple bend in the harness improves the purchase of the attaching tape.
Fig. 2. Harnessing the mouse, a) Dimensions of the tapes, b) Attaching the first bandage. c) Attaching the harness, d) Attaching the cross-tape, e) Harnessed mouse.
66
Figure 2 lit
a) The tape is ~ Micropore tape (1.25 cm Hypoallergenic microporous No. 1530, 3 M Co., St. Paul, Minnesota, U.S.A.). Note that the tapes are laid o u t sticky side up. b,c) The long tag of the first tape provides an attachment for the harness. d) The cross piece helps to restrict twisting movements and prevents the mouse working loose from the bandage.
Figure 3 a, b, c ) A n infusion line runs above the platform; a bar carrying water bottles to the side of it. Just below the platform is shown a padded heating rod (a, c); this is normally clamped at mouse height (b). Below the platform a cooled test tube is suspended from a pipe carrying a cooled water supply. A repair station is also shown (a), consisting of a movable arm, to hold the harness, and a mouse stand. This is useful for attending to cannulae, etc. The swivels in the infusion line (Ferraris Development and Engineering Co. Ltd., 26 Lea Valley Trading Estate, London N18, U.K.) may also be available from Dr. B.M. Wright, Department of Bio-Engineering, Clinical Research Centre, Harrow, Middlesex HA1 3UJ, U.K. The apparatus shown for cooling the collecting test tube consists of two perspex tubes, insulated by polyurethane foam, with multiple outlets. Water at 4--6°C is pumped along the upper pipe and circulated to the lower one through silicone rubber tubing (Esco Rubber, Ltd., 14--16 Great Portland St., London, WIN 5AB, U.K.), wrapped on a cardboard former around the test tube. The tubing is secured
I
:
USION BOTTLES
REPAIR
PRMS
Harness G ~ed )
Mouse
ZTION
Tier 2
67
line
~ottle
Heating rod
(at mouse level )
Infusior Swivel In-line Swivel
Thoraci, ca!
rod ped )
Wire su Hose cli I Test tub Cardbo~ Cooling
)LING : ~ipe
pip
68
SALINE i~_~-Sw
i:~, ~
ve I j o i n t
26G/21G
Adaptor
E Fig. 3. a, b, e, d, e. See t e x t .
to the inlet and outlet pipes with Unex hose clips (Jencons (Scientific) Ltd., Maple Road, Hemel Hempstead, Herts, HPZ 7DE, U.K.). Heating is by means of 1" Electrothermal Heating Tape (Baird and Tatlock (London} Ltd., P.O. Box 1, Romford, Essex RM1 1HA, U.K.}, threaded through a brass rod, which is wrapped in asbestos tape and covered by cotton wool and stocking gauze. d, e ) F o r flexibility a length of fine nylon tubing (0.5 mm o.d. Portex FLEXOO 800/200/100/700, Portex Ltd., Hythe, Kent, U.K.) is inserted in the infusion line between the swivel arm and the intravenous cannula, using adaptors made from 26 G and 21 G syringe needles glued together. The mice
69 then pay no attention to their tails and the cannulae need no special protection. Mouse food is simply scattered on the platform. APPENDIX: ON INTRAVENOUS CANNULATION IN MICE Metal cannulae, e.g. lengths of hypodermic needle, have been employed for short-term intravenous infusion; however, they readily penetrate vein, walls unless the mice are severely restrained. Fine polythene cannulae avoid this problem. They can be hand-drawn from 1.0--1.5 mm tubing (Portex PP 55 or PP 60: Portland Plastics, available from Southern Syringe Services Ltd., Chase Road, L o n d o n N14 6JV, U.K.}, using a microburner with a 1--2 mm flame. Short cannulae, 2.0--2.5 cm from tip to shank, lie in a lateral tail vein and can be inserted with little difficulty. These are satisfact o r y for fairly slow infusions at about 0.12 ml/h; and although much higher flow rates than this are possible continuous infusion at rates around 1 ml/h cannot be reliably sustained for more than 4--5 days; because the vein wall tends to break down. Long cannulae have been used for prolonged infusion over 5--6 weeks at rates down to 0.5 ml/24 h -- a length of 7.0--7.5 cm reaches the inferior vena cava -- and for cardiac catheterisation (13.0-13.5 cm reaches the right ventricle). The cannulation technique is more demanding for these, however; and they tend to become blocked with fine debris produced by the pump after 10--15 days unless an in-line filter is included. A small spring-clip fitting holding a 5 mm diam filter is produced by Ferraris Development and Engineering Co. Ltd. (26 Lea Valley Trading Estate, L o n d o n N.18, U.K.).
Cannulation technique Figs. 4, 5 and 6 illustrate the main points of the technique for short (fig. 4) and long (figs. 5 and 6) cannulae, respectively. The following notes amplify certain points:
Short cannulae, fig. 4 a) The cannula is angled onto the shank, and should have an o.d. n o t greater than about 0.1 mm (at 0.15 mm o.d. it is too rigid and likely to strip up the vein). The trocar is a shallow 21 SWG half-needle. b) The mouse is placed in a warm cage for 5--10 min; then transferred to a mouse holder underneath a 300 W lamp; the tail is bent around the forefinger at a point as far distally as possible; and the trocar is pushed straight towards the vein, without angling, until blood wells up in it. c) If the cannula fails to pass beyond the trocar tip the trocar is edged slightly forward before trying again. d) After drying the tail, tape is folded around the tail and shank of the cannula; overlapping pieces are taped above and below this and trimmed. The cannula is tested for position and patency by delivering 0.25--0.5 ml of
70
....i"'!"l'i"r'"['"~'"i"l'i'!"'~'¸ I" 'l"i 2
3
~
5
6
7
"'L''i''~" ~i' "~"~...... 8
9
~0
1~
!i
~E
Fig. 4. S h o r t c a n n u l a e , a) D i m e n s i o n s of t h e c a n n u l a a n d trocar, b) I n s e r t i n g t h e trocar~ c) I n s e r t i n g t h e c a n n u l a , d) T a p i n g t h e c a n n u l a i n t o place, e) T h e t a p e d c a n n u l a .
saline into the vein. Profuse bleeding may sometimes prevent the tape attaching securely to the tail. This is best avoided by not overheating the mouse; but it can be counteracted to some extent by injecting cold saline into the cannula. If this fails it is best to put the mouse aside, even with the fastenings insecure, in order to cool off. Within 15--30 min the mouse can then be retaped. The cannula is usually easily replaced in position if dislodged.
71
Long cannulae, fig. 5 Cannulae are best made freshly or kept under liquid e.g. 70% alcohol, to prevent their becoming inextricably entangled. They can sometimes be inserted with the half-needle trocar, as are short cannulae; but their extreme flexibility usually makes the special needle necessary. Note that the figure shows the needle (23 SWG -1!"~ -2 2 , cut down at right angles to the plane of the bevel. The needle holder is about 9 cm in length.
Fig. 6 a) The cannula is threaded into the needle just short of the bevel; the mouse is well warmed and anaesthetised wi~h ether. b) The needle enters the vein with the bevel upwards; then passes along the vessel; and is rotated and pushed out of the vein with the bevel facing down, in this way piercing the wall cleanly. c) The needle is drawn out towards the base of the tail. d) The cannula is inched into the vein with thumb and forefinger, the fingers peeling off the cannula forwards towards the base of the tail. Occasionally the cannula fails to get beyond the point where the needle exited; this can usually be overcome by gently squeezing the tail at this point, provided the vein has been adequately dilated at the beginning. (During cardiac catheterisation a block is not infrequently encountered somewhere in the course of the inferior vena cava. This can sometimes be negotiated after allowing the mouse to kick about in recovering from the anaesthetic.) An alternative m e t h o d to the techniques of figs. 5 and 6 has been used in recent work for inferior vena caval cannulation. This takes longer, but is easier, and avoids the need for anaesthetising the mouse. Precannulation with a short cannula is carried out; and after an hour or so, when a track into the tail vein has been established, the cannula is removed and immediately replaced by the indwelling long cannula, using the technique shown in fig. 6d.
m
-112
Fig. 5. Special needle and needleholder for long cannulae.
72
D
Fig. 6. Long cannulae, a) Introducing the needle, b) Positioning the cannula for catherisation. c) Withdrawing the needle, d) Catherisation. ACKNOWLEDGEMENT I s h o u l d like to a c k n o w l e d g e the valuable help o f the P h o t o g r a p h i c D e p a r t m e n t s o f T h e L o n d o n Hospital and the Medical College. REFERENCES Bainbridge, D.R. and B.M. Wright, 1965, J. Physiol. 177, 6P. Boake, J.L. and M.F.A. Woodruff, 1965, Nature 205,396. BoUman, J.L., J.C. Cain and J.H. Grindley, 1948, J. Lab. Clin. Med. 33, 1348. Gesner, B.M. and J.L. Gowans, 1962, Brit. J. Exp. Pathol. 43,424. Shrewsbury, M.M., 1959, Proc. Soc. Exp. Biol. Med. 101,492. Sprent, J., 1973, Cell Immunol. 7, 10.
63
© Elsevier/North-Holland Biomedical Press
T H E MOUSE CIRCUS: A SIMPLE APPARATUS FO R THORACIC DUCT
C A N N U L A T I O N AND CONTINUOUS I N TRA V E N O U S INFUSION
D.R. BAINBRIDGE
Department of Immunology, London Hospital Medical College, London, E1 2AD, U.K.
(Received 18 December 1976, accepted 18 March 1977)
A simple apparatus is described for maintaining mice during thoracic duct cannulation and/or continuous intravenous infusion, which involves much less restraint than current methods. An Appendix describes the techniques of intravenous cannulation which have been used for prolonged infusion or cardiac catheterisation.
INTRODUCTION Thoracic d u c t cannulation in rodents, first introduced for rats by Bollman et al. (1948) and successfully applied in mice by several workers (Shrewsbury, 1959; Gesner and Gowans, 1962; Boake and Woodruff, 1965; Sprent, 1973} continues to play an i m p o r t a n t part in investigating the role of l y m p h o c y t e s in i m m une responses. Current practice, however, involves severely restraining the animal's f r e e dom of m o v e m e n t ; given the sensitivity of l y m p h o c y t e s to stress steroids this m ay be unfavorable. The apparatus described here, a 'circus' rather than the cust om ary mouse 'wheel', was devised to keep the restraint on cannulated mice to a minimum; it is moreover mu ch simpler to construct. In principle it consists of a (perspex) platform bearing a central pillar made from a length of glass tubing in a r u b b er bung, which carries a freely rotating arm made from coiled wire. A wire harness is attached to the arm by a swivel clip and is taped to the mouse. This allows the animal considerable liberty to move in any direction e x c e p t a 180 ° twist. The thoracic duct cannula is threaded, out of the way, t h ro u g h the centre t ube to a collecting vessel underneat h the platform. Intravenous infusion during the first 24 h after cannulation, as r e c o m m e n d e d by Sprent (1973) for salt replacement, can be carried out using the mouse circus, if a mercury-sealed swivel j oi nt (Bainbridge and Wright, 1965) is e m p l o y e d in the infusion line. F o r sustained infusion the circus is more satisfactory than the tailtethering m e t h o d briefly described by Bainbridge and Wright (1965), at least when the latter is used with swivel joints available commercially. These have proved to require much greater t o r q u e than original examples o f the design, m o r e than mice can readily apply at the tip o f their tails.
64
The platforms can be conveniently placed on scaffolding constructed from Climpex Tubing (Baird and Tatlock, London, Ltd, P.O. Box 1, Romford, Essex RM1 1HA, U.K.). A circus assembly in current use in this laboratory consists of 3 tiers, each of 8 platforms set side by side, accommodating 24 mice at a time. The infusion lines are supplied by simple multichannel deltaperistaltic pumps (modified from Bainbridge and Wright (1965). Commercial variations on the design are sold as Watson--Marlow pumps, Fisons Scientific Apparatus Ltd., Loughborough, Leicestershire, U.K.), with individual or c o m m o n reservoirs as required. D E S C R I P T I O N O F THE A P P A R A T U S
Figures 1, 2 and 3 illustrating the construction of the apparatus and installation of the mouse are largely self-explanatory. The following comments are intended to amplify certain points.
Figure 1 a) Paper is wrapped around the platform and held in place by a small bung, which also serves to prevent the platform sliding a b o u t on the scaf-
D
........i....... ~i'~'~i'i'i~"!~'~l'~!
'~! ~'1¸~¸~¸~''~¸¸¸¸~ ...............
Fig. 1. C o n s t r u c t i o n o f a p p a r a t u s , a) D i m e n s i o n s o f t h e p l a t f o r m and pillar, b) Construct i o n o f t h e swivel and harness, c) A s s e m b l y o f swivel on the pillar.
65 folding. When dirty t he platform can be changed easily for a new one, if need be while the mouse is in place. b) T w e n t y - o n e SWG stainless steel wire is w o u n d around an iron bar of suitable diameter to make the coil. The slide at one end of the coil and the rings on the extension arm at the ot her are made using small round-tipped pliers and wire-snips. The slide enables the coil to rot at e freely back and forwards. The triple bend in the harness improves the purchase of the attaching tape.
Fig. 2. Harnessing the mouse, a) Dimensions of the tapes, b) Attaching the first bandage. c) Attaching the harness, d) Attaching the cross-tape, e) Harnessed mouse.
66
Figure 2 lit
a) The tape is ~ Micropore tape (1.25 cm Hypoallergenic microporous No. 1530, 3 M Co., St. Paul, Minnesota, U.S.A.). Note that the tapes are laid o u t sticky side up. b,c) The long tag of the first tape provides an attachment for the harness. d) The cross piece helps to restrict twisting movements and prevents the mouse working loose from the bandage.
Figure 3 a, b, c ) A n infusion line runs above the platform; a bar carrying water bottles to the side of it. Just below the platform is shown a padded heating rod (a, c); this is normally clamped at mouse height (b). Below the platform a cooled test tube is suspended from a pipe carrying a cooled water supply. A repair station is also shown (a), consisting of a movable arm, to hold the harness, and a mouse stand. This is useful for attending to cannulae, etc. The swivels in the infusion line (Ferraris Development and Engineering Co. Ltd., 26 Lea Valley Trading Estate, London N18, U.K.) may also be available from Dr. B.M. Wright, Department of Bio-Engineering, Clinical Research Centre, Harrow, Middlesex HA1 3UJ, U.K. The apparatus shown for cooling the collecting test tube consists of two perspex tubes, insulated by polyurethane foam, with multiple outlets. Water at 4--6°C is pumped along the upper pipe and circulated to the lower one through silicone rubber tubing (Esco Rubber, Ltd., 14--16 Great Portland St., London, WIN 5AB, U.K.), wrapped on a cardboard former around the test tube. The tubing is secured
I
:
USION BOTTLES
REPAIR
PRMS
Harness G ~ed )
Mouse
ZTION
Tier 2
67
line
~ottle
Heating rod
(at mouse level )
Infusior Swivel In-line Swivel
Thoraci, ca!
rod ped )
Wire su Hose cli I Test tub Cardbo~ Cooling
)LING : ~ipe
pip
68
SALINE i~_~-Sw
i:~, ~
ve I j o i n t
26G/21G
Adaptor
E Fig. 3. a, b, e, d, e. See t e x t .
to the inlet and outlet pipes with Unex hose clips (Jencons (Scientific) Ltd., Maple Road, Hemel Hempstead, Herts, HPZ 7DE, U.K.). Heating is by means of 1" Electrothermal Heating Tape (Baird and Tatlock (London} Ltd., P.O. Box 1, Romford, Essex RM1 1HA, U.K.}, threaded through a brass rod, which is wrapped in asbestos tape and covered by cotton wool and stocking gauze. d, e ) F o r flexibility a length of fine nylon tubing (0.5 mm o.d. Portex FLEXOO 800/200/100/700, Portex Ltd., Hythe, Kent, U.K.) is inserted in the infusion line between the swivel arm and the intravenous cannula, using adaptors made from 26 G and 21 G syringe needles glued together. The mice
69 then pay no attention to their tails and the cannulae need no special protection. Mouse food is simply scattered on the platform. APPENDIX: ON INTRAVENOUS CANNULATION IN MICE Metal cannulae, e.g. lengths of hypodermic needle, have been employed for short-term intravenous infusion; however, they readily penetrate vein, walls unless the mice are severely restrained. Fine polythene cannulae avoid this problem. They can be hand-drawn from 1.0--1.5 mm tubing (Portex PP 55 or PP 60: Portland Plastics, available from Southern Syringe Services Ltd., Chase Road, L o n d o n N14 6JV, U.K.}, using a microburner with a 1--2 mm flame. Short cannulae, 2.0--2.5 cm from tip to shank, lie in a lateral tail vein and can be inserted with little difficulty. These are satisfact o r y for fairly slow infusions at about 0.12 ml/h; and although much higher flow rates than this are possible continuous infusion at rates around 1 ml/h cannot be reliably sustained for more than 4--5 days; because the vein wall tends to break down. Long cannulae have been used for prolonged infusion over 5--6 weeks at rates down to 0.5 ml/24 h -- a length of 7.0--7.5 cm reaches the inferior vena cava -- and for cardiac catheterisation (13.0-13.5 cm reaches the right ventricle). The cannulation technique is more demanding for these, however; and they tend to become blocked with fine debris produced by the pump after 10--15 days unless an in-line filter is included. A small spring-clip fitting holding a 5 mm diam filter is produced by Ferraris Development and Engineering Co. Ltd. (26 Lea Valley Trading Estate, L o n d o n N.18, U.K.).
Cannulation technique Figs. 4, 5 and 6 illustrate the main points of the technique for short (fig. 4) and long (figs. 5 and 6) cannulae, respectively. The following notes amplify certain points:
Short cannulae, fig. 4 a) The cannula is angled onto the shank, and should have an o.d. n o t greater than about 0.1 mm (at 0.15 mm o.d. it is too rigid and likely to strip up the vein). The trocar is a shallow 21 SWG half-needle. b) The mouse is placed in a warm cage for 5--10 min; then transferred to a mouse holder underneath a 300 W lamp; the tail is bent around the forefinger at a point as far distally as possible; and the trocar is pushed straight towards the vein, without angling, until blood wells up in it. c) If the cannula fails to pass beyond the trocar tip the trocar is edged slightly forward before trying again. d) After drying the tail, tape is folded around the tail and shank of the cannula; overlapping pieces are taped above and below this and trimmed. The cannula is tested for position and patency by delivering 0.25--0.5 ml of
70
....i"'!"l'i"r'"['"~'"i"l'i'!"'~'¸ I" 'l"i 2
3
~
5
6
7
"'L''i''~" ~i' "~"~...... 8
9
~0
1~
!i
~E
Fig. 4. S h o r t c a n n u l a e , a) D i m e n s i o n s of t h e c a n n u l a a n d trocar, b) I n s e r t i n g t h e trocar~ c) I n s e r t i n g t h e c a n n u l a , d) T a p i n g t h e c a n n u l a i n t o place, e) T h e t a p e d c a n n u l a .
saline into the vein. Profuse bleeding may sometimes prevent the tape attaching securely to the tail. This is best avoided by not overheating the mouse; but it can be counteracted to some extent by injecting cold saline into the cannula. If this fails it is best to put the mouse aside, even with the fastenings insecure, in order to cool off. Within 15--30 min the mouse can then be retaped. The cannula is usually easily replaced in position if dislodged.
71
Long cannulae, fig. 5 Cannulae are best made freshly or kept under liquid e.g. 70% alcohol, to prevent their becoming inextricably entangled. They can sometimes be inserted with the half-needle trocar, as are short cannulae; but their extreme flexibility usually makes the special needle necessary. Note that the figure shows the needle (23 SWG -1!"~ -2 2 , cut down at right angles to the plane of the bevel. The needle holder is about 9 cm in length.
Fig. 6 a) The cannula is threaded into the needle just short of the bevel; the mouse is well warmed and anaesthetised wi~h ether. b) The needle enters the vein with the bevel upwards; then passes along the vessel; and is rotated and pushed out of the vein with the bevel facing down, in this way piercing the wall cleanly. c) The needle is drawn out towards the base of the tail. d) The cannula is inched into the vein with thumb and forefinger, the fingers peeling off the cannula forwards towards the base of the tail. Occasionally the cannula fails to get beyond the point where the needle exited; this can usually be overcome by gently squeezing the tail at this point, provided the vein has been adequately dilated at the beginning. (During cardiac catheterisation a block is not infrequently encountered somewhere in the course of the inferior vena cava. This can sometimes be negotiated after allowing the mouse to kick about in recovering from the anaesthetic.) An alternative m e t h o d to the techniques of figs. 5 and 6 has been used in recent work for inferior vena caval cannulation. This takes longer, but is easier, and avoids the need for anaesthetising the mouse. Precannulation with a short cannula is carried out; and after an hour or so, when a track into the tail vein has been established, the cannula is removed and immediately replaced by the indwelling long cannula, using the technique shown in fig. 6d.
m
-112
Fig. 5. Special needle and needleholder for long cannulae.
72
D
Fig. 6. Long cannulae, a) Introducing the needle, b) Positioning the cannula for catherisation. c) Withdrawing the needle, d) Catherisation. ACKNOWLEDGEMENT I s h o u l d like to a c k n o w l e d g e the valuable help o f the P h o t o g r a p h i c D e p a r t m e n t s o f T h e L o n d o n Hospital and the Medical College. REFERENCES Bainbridge, D.R. and B.M. Wright, 1965, J. Physiol. 177, 6P. Boake, J.L. and M.F.A. Woodruff, 1965, Nature 205,396. BoUman, J.L., J.C. Cain and J.H. Grindley, 1948, J. Lab. Clin. Med. 33, 1348. Gesner, B.M. and J.L. Gowans, 1962, Brit. J. Exp. Pathol. 43,424. Shrewsbury, M.M., 1959, Proc. Soc. Exp. Biol. Med. 101,492. Sprent, J., 1973, Cell Immunol. 7, 10.
