Oil the Blood and Animal Tissues. 133 



The following measurements by former observers are given 

 for the sake of comparison. 



Jurine 52T0 



Jiirine in a 2d measurement . -^-^-^q 



Bauer y^o^y 



WoUaston 3-^00 



Young g rjVo 



Kater ^jo^oo 



Ditto eo'jjjj 



Prevost and Dumas ToVb^ 



The thickness of the particles, which is perhaps not so luii- 

 form as the diameter of the disks, is on an average to this latter 

 dimension as 1 to 45. 



The form and size of the particles of the blood of other 

 animals have frequently been compared with those of man. 

 Many observations were made for this purpose by Hewson ; 

 but while some of them appear tolerably accurate, others are 

 decidedly far from the truth. Those which have recently 

 been made by Prevost and Dumas, are the most extensive and 

 complete which as yet exist. Our attention having been 

 chiefly taken up with the blood of man, we have not as yet 

 carried our investigation of that of other animals so far as we 

 design doing; we have, however, examined the blood in all 

 the classes of vertebrate animals, and in different species of 

 most of them. Our observations completely accord with those 

 of Prevost and Dumas, as to the particles having a circular 

 form in the mammalia, and an elliptical one in the other three 

 classes. There are varieties both in the size and proportion 

 of the particles in different species. Thus for example, in the 

 pig and rabbit, the particles have a less diameter, but a greater 

 thickness than in man. We have hitherto invariably found 

 the elliptical j^articles larger than the circular, but they are 

 proportionably thinner. In birds, the particles are much 

 more numerous, but smaller than in either reptiles or fishes. 



Tliere are numerous interesting phaenomena which present 

 themselves when the particles lose their integrity and assume 

 new forms. Changes of this description are occasioned by the 

 spontaneous decomposition which the blood undergoes a 

 longer or shorter time after its escape from the body, by me- 

 chanical violence, and by the addition of various substances, 

 which appear to exert a chemical action on the matter of 

 which the particles are composed. To these appearances we 

 iiave been induced to devote the more attention, from their 

 seeming calculated to throw some light on the compt)sition 

 and structure of the particles. We were also desirous ol 

 not hastily or lashly denying the existence of those colour- 

 less 



