PHYSIOLOGY. 197 



CCLIX. These are conjectures concerning the parts of 

 animal blood ; and it remains to say in what proportion each of 

 them is present in it. This will perhaps be always difficult ; 

 and in the mean time we can perceive, that many estimates for- 

 merly made could not be exact, as the several parts were not 

 properly known ; and, while judging chiefly from the appear- 

 ances upon spontaneous separation, physicians were not aware 

 how much these are affected by the circumstances of extravasa- 

 tion, and by those in which the blood is placed after being 

 drawn out. There are not yet indeed experiments made to as- 

 certain, with any exactness, the proportion of the several parts 

 mentioned ; but it is probable, that the red globules make a 

 small part of the whole ; that the gluten, if we consider both 

 what is in the crassamentum and in the serum, is In much 

 larger proportion, but that the watery portion is the largest of 

 all, and at the same time that this has always a considerable 

 quantity of saline matter dissolved in it. 



" That the red globules may be in different proportions to 

 the whole mass, we discern very clearly from several diseases, 

 in which their quantity is evidently and considerably diminish- 

 ed ; but what may be their proportion in persons in health, or 

 in what manner that proportion is connected with the other cir- 

 cumstances of health, is by no means ascertained by any pro- 

 per experiments. From several observations on animals whose 

 vessels are easily subjected to microscopical examination, it ap- 

 pears that the proportion of red globules is greater or lesser, ac- 

 cording to the greater or lesser quantity of the aliment or nour- 

 ishment the animal receives. It is very possible, therefore, 

 that the quantity of them in the human blood may be affected by 

 the same circumstances ; but still this does not aid us in deter- 

 mining the question with respect to persons in health, who take 

 in nourishment in proportion to their several bulks; and whether 

 the effect of nourishment be determined by the quality, as well 

 as by the quantity, is not ascertained. It appears to me, that, if 

 at all, it is not affected much by the quality of nourishment, 

 unless the difference of that quality be very considerable. It 

 appears also, that the proportion of red globules is as great in 

 the animals living entirely upon vegetable aliment, as it is in 



