336 Dr. A. du Pre Denning and Mr. J. H. Watson. [May 7, 



Fig. 4. — Accessory Pressure Apparatus. 



Details of Experimental Results. 



For the immediate purpose of these laboratory experiments, horses' blood 

 was employed, since the corpuscular elements in such blood have been 

 estimated by Sir John McFadyean to be practically identical in shape, though 

 slightly less (in size) than those of human blood, viz., about 7 yu. in diameter, 

 and, moreover, horses' blood has this distinct advantage that, after an anti- 

 coagulator has been added to it, the corpuscles and other cellular bodies are 

 comparatively quick in settling, and soon leave a reasonably clear plasma. 

 The objection may, perhaps, be raised that experiments carried out with 

 animal blood are not, strictly speaking, applicable to human beings, but, as 

 will be shown in the sequel, such results, although not numerically applic- 

 able, cannot but inevitably lead to deductions and conclusions, the principles 

 of which are as fundamentally true for human physiology as for animal 

 physiology. 



Considering the heterogeneous structure of blood in general, and how 

 variously the constituents of the blood of individual members of any one 



