322 



Fi*. 2. 



man's instrument, nor is it immediately turned in a direction at right 

 angles to the one it was previously pursuing ; on the contrary, the de- 

 viation from the natural course is gradual, and the fluid is coaxed, as it 

 were, round the turns in the tube, when it arrives at them. I have 

 already mentioned that the caliber of the tube equals that of the artery 

 when at a moderate expansion, and also that the caliber of the turns 

 of the tube is very slightly wider than the caliber of the straight por- 

 tions. I need not again repeat why these differences in caliber should 

 exist. From the foregoing remarks you have already anticipated the 

 necessity for having different tubes, each with a different bore, so as 

 to be applicable in the case of variously-sized arteries. I have de- 

 scribed to you Yolkman's arrangement of cone-shaped cups for connect- 

 ing his tube to the ends of the arteries. I do not recognise the 

 necessity for this plan at all ; and I believe that, if the glass tube have 

 its termination furnished with slightly raised edges, so as to take a pur- 

 chase on the artery, the desired effect is obtained just as well. 



The removal from or fastening of the different tubes to the support 

 is easily effected by opening and shutting the fasteners (Fig. 1 

 which are furnished with hinges and clasps. 



Each tube is fur- 

 nished with a piston 

 index apparatus (c), 

 and with astopcock(^). 

 The piston index ap- 

 paratus (Figs. 2 and 3), 

 consists of two tubes, 

 the one horizontal, 

 whose bore equals 

 that of the glass 

 tube, and which is 

 continuous with it ; 

 the other perpendi- 

 cular, arising from 

 the centre of the for- 

 mer, and into which 

 fits exactly a piston. 

 This latter tube, in- 

 stead of being round- 

 ed, as is the horizontal tube, is square. Where the two tubes commu- 

 nicate, therefore, a square orifice exists in the upper wall of the hori 

 zontal one (Fig. 4); ~ 4 



so that, were fluid tra- 

 versing this latter, it 

 would rush up into 

 the square perpendi- 

 cular tube. The handle of the piston consists of the stem, the pres 

 and the handle proper. The stem is of such lengthy that, when th 

 piston is shut down, the press, or lower surface of it, must form 



