THE BLOOD. 73 



The inflammatory crust or size is not a new-formed sub- 

 stance (XLII), but is merely the coagulable lymph separated 

 from the rest of the blood. This separation seems to be occa- 

 sioned by the lymph being attenuated (XLIII), by which means 

 the red particles soon settle to the bottom, and leave the sur- 

 face of the blood transparent ; and this transparent part being 

 a mixture of the coagulable lymph and the serum, the former 

 coagulates on its surface where, in contact with the air, and the 

 disposition to coagulate being likewise diminished, the blood 

 remains a long time fluid, and thereby gives time for the pel- 

 licle formed on its surface to attract the rest of the lymph, and 

 to collect it at the top, leaving the bottom of the cake propor- 

 tionably softer (XLIV). The size therefore is thicker and 

 denser, in proportion as the lymph is thinned (XLV), and is less 



(XLII.) Dr. Benjamin G. Babington a concludes that fibrin and serum 

 do not exist as such in the circulating blood, but that this is composed 

 only of corpuscles and of a homogeneous liquor sanguinis ; that there 

 is no such animal fluid as coagulable lymph, since the liquor sanguinis 

 is essentially liquid, separating indeed under certain conditions into two 

 parts, of which one only is spontaneously coagulable ; and that there is 

 no better reason for affirming that fibrin exists in a fluid state in the 

 liquor sanguinis than for affirming that muriatic acid exists in a solid 

 state in muriate of ammonia. But it is difficult to reconcile Dr. Ba- 

 bington's conclusion with the fact, admitted by him, that serum differ- 

 ing very little from that of the blood, and unaccompanied by fibrin, is 

 not unfrequent in the serous cavities ; which fact, as Dr. Davy remarks 5 , 

 agrees with the opinion of Hewson and Hunter, that the fluid part of 

 the blood is an equable mixture of lymph and serum, one spontaneously 

 coagulable and the other not. The specific gravity of some pellucid 

 serum which I took from a hydrocele was as high as 1024- 



(XLIII.) See Notes xxm and xxix. 



(XLIV.) The influence here attributed to the attraction of the pellicle 

 is doubtful, because the rising of the fibrin, and the difference of con- 

 sistency in the upper and lower parts of the clot, may be accounted for 

 by the sinking of the corpuscles. When the liquor sanguinis of the 

 horse is removed from the corpuscles, and allowed to coagulate in a 

 tube, I find that the upper and lower parts of the clot do not differ in 

 consistency. The observations of Dr. Davies on the specific gravity of 

 the different parts of the blood are noticed in the Introduction. Dr. 

 Davy c found the specific gravity of a mixture of human red corpuscles 

 and serum, obtained by straining the broken-up clot through linen, to 

 be 10/4 ; of the cruor drained of serum 1087 ; of the bufly coat, by 

 weighing, 1060; of the corpuscles, by immersion in a saline solution, 



a Med. Chir. Trans, vol. xvi, p. 301. c Researches, Physiol. and Anat. ii, 17-20. 

 b Researches, Physiol. and Anat. ii, 21. 



