198 PHYSIOLOGY. 



those who live entirely upon animal food, or as it is in man, 

 who lives partly upon the one and partly upon the other. 



" Many attempts have been made to estimate the proportion 

 of the quantity of the crassamentum to that of the serum in the 

 extravasated human blood ; but hardly any of the experiments 

 yet made afford a certain conclusion. The apparent proportion 

 of the two masses is very fallacious ; being very much varied 

 by the circumstances which determine the concretion of the 

 cruor to take place sooner or later, and by the time which is 

 allowed to pass from the time of concretion to that at which the 

 proportions are examined. It is now indeed well known, that 

 these circumstances vary the separation which takes place ; and 

 it does not appear to me, that in any of the estimates which have 

 been made, due attention has been given to the effect of those 

 circumstances. When Dr. Haller, in his Primce Linece, 

 ( 138.) gives his judgment : ' In massa sanguinea media 

 pars, et ultra, cruoris est. In robore valido serum minuitur 

 ad tertiam partem, in febre ad quartam et quintam reducitur, 

 in morbis a debilitate increscit ;' I am persuaded that he had 

 judged^entirely from the quantities that appear separated in or- 

 dinary blood-lettings, and had not attended to the different 

 quantities that appear in these according to the different circum- 

 stances of the blood-letting. In cases of rheumatism, I have 

 seen the crassamentum not equal to a third part of the serum 

 surrounding it ; and other cases, where the serum did not sepa- 

 rate from the crassamentum, to the amount of a fourth part of the 

 whole mass; and from attending to the circumstances of the 

 blood-letting, I have been able to foretel what, in twenty-four 

 hours after, would be the condition of the separation. But even 

 supposing we had a more exact estimate of the serum with re- 

 spect to the crassamentum, or in other words, of the red glo- 

 bules and gluten taken together, it still remains undetermined 

 what proportion these two last mentioned matters bear to one 

 another ; and consequently it is not yet ascertained what is the 

 usual proportion of red globules in the blood of persons in 

 health, nor how far it may have a share in producing a peculiar 

 temperament. 



" With respect to the gluten of the blood, considered by 



