310 Addis 



state of slight agglutination into which it passes whenever it leaves 

 tlie vessels. 



That the inertia of the corpuscles is not the only factor is shown by the 

 fact that the initial pressure required varies according to the time the blood 

 is left exposed to the action of the air. If this time is 2 or 3 minutes, it is 

 often found that a pressure of four or five times the standard pressure is 

 not sufficient to start the flow. 



In different individuals, also, there seem to bo slight variations in the 

 rate at which the blood agglutinates. 



If the technique as regards the taking of the blood is strictly 

 observed, it will be found that a height of slightly more than twice 

 the standard pressure will act uniformly. Thus, with my present ap- 

 paratus, in which the standard pressure is represented by a height of 

 reservoir above the blood of 10 cm., an initial height of 20 to 22 cm. 

 is required. 



The outline of the drop, as the reservoir is being raised, should be 

 watched. When the agglutination has been overcome, a tongue of blood is 

 seen to stream out from the drop. The reservoir is, then, at once lowered ; 

 but it shoukl be done slowly, so as gradually to lessen the rate at which the 

 corpuscles are revolving. 



When the low power is brought into its focal position, the lens lies only 

 a few millimetres above the top of the glass cone, and is immersed in the oil 

 which flows out of the chamber. If the necessary conditions have been 

 observed, the corpuscles are seen streaming round fairly rapidly, each one 

 separate from the other. The part where the flow is most rapid is the 

 point at which the oil stream impinges on the blood. This is the part 

 which should be watched. After about 7 minutes have elapsed with 

 out any observable change, one or two stationary streaks appear a 

 little way from the edge of the drop. These rapidly increase in number 

 and length, and with this there is an appreciable diminution in the rate 

 of flow. 



Within a half to one minute more, the streakiness will have extended 

 right up to the edge, and there will now form a laminated clot, within the 

 meshes of which more and more corpuscles become entangled. Only a 

 small part of the total number of corpuscles continue to flow slowly and 

 interruptedly round. 



The signs of a clot associated with the cessation of flow of the great 

 body of the corpuscles, is the end-point adopted. When this is attained the 

 time is again taken and the estimation is complete. 



To a greater or a less extent all the conditions necessary for accurate 

 results are realised in this method. There is one essential which is not 

 fully carried out in any other raethod, but which is perfectly complied with 

 in this, i.e. the maintenance of a constant temperature in all comparative 

 observations. 



The temperature of the blood, as it comes from the capillaries is about 



I 



I 



