142 APPENDIX 



Connecting Artery with Manometer. 



Every teacher will have his own manipulative procedure ; that described merely 

 exemplifies one of several plans of routine which may be adopted. What is of importance 

 is that the student should have practice and attain skill in a reliable routine. Following the 

 above instructions students do in fact obtain very uniform success. A mistake they tend to 

 at first is to leave open, after connecting the artery with the manometer, the clamp on the tube 

 from the reservoir pressure-bottle ; this is of course, unless immediately remedied, fatal to 

 the preparation, especially if the solution used be MgSO^. MgSO^ (half saturated) proves, 

 however, more effectual than NagSO^ (half-saturated) as a preventive of clotting. I have 

 seen student's carotid records running for 2| hours without their having met with any inter- 

 ruption from clotting. 



In providing arterial cannulae it is well to make them of variously sized nozzle, but all 

 from glass tubing of one size, e. g. 3 mm. external diameter, fitting the rubber pressure-tubing 

 of 2-5 mm. bore. The cannulae are straight and short, e. g. 3 cm. length. The bulbous 

 cannulae with side-branch, which are less easily made and more expensive to buy, are not a 

 necessity. Neither is the steel bulldog clip for occluding the artery while the cannula is 

 being inserted and the junction with manometer made. The instructions omit it, its place 

 being taken by the thread-loop weighted at the time required by the ordinary artery-forceps 

 or the clip of a string-weight. Objections to the bulldog clip are that, in students' hands 

 at least, it is more likely to do damage and lead to clotting than is the thread-loop, and that, 

 on account of its small size and liability to be left by the student in the wound, it is apt to 

 be lost, e. g. thrown away with the carcase when the tables are cleared after the class- 

 meeting. A recurrent item of expense in working the class is avoided by dispensing with 

 the bulldog clip. 



It may be noted that with the technique given a student can, if need be, e. g. during a 

 class examination, perform an arterial-pressure experiment single-handed and entirely 

 unaided. 



The operative steps in preparation for the arterial-pressure record, &c., are preferably 

 done with the table shifted a few feet from the kymograph, although the latter has been got 

 ready. Otherwise the student is hampered by the kymograph, and the manometer, float, 

 guides, &c., may be disturbed. After the operation the table is brought up close to kymo- 

 graph. The rubber pressure-tube, junctional between manometer and arterial cannula, can 

 without disadvantage have 60 cm. length. 



Intravenous Injedion. 



Students find more difficulty with the intravenous injection, hence the importance of 

 the instruction to them to take a distal point of the exposed vein for insertion of the needle- 

 syringe, so allowing, in case of a failure at a first attempt, the opportunity of a reattempt more 

 proximally. 



Obs. 20. For faradization of the spinal cord. The procedure given departs somewhat 

 widely from that usually followed, e. g. HandbJc. of the Physiol. Lah. (Burden Sanderson), 

 p. 240, but presents the following advantages : (1) No general convulsion is caused and 

 therefore curare is not required ; (2) the precise seat of stimulation of the cord is seen and 

 can be confined to the most effective point, namely, lateral column, exposed in transverse 



