OF THE COAGULATION OF THE BLOOD. 57 



the globules of the blood ; but they do not admit with him that the red globules undergo 

 a rapid change after they escape from the vessels, or that the colouring matter which en- 

 velopes the central spherical body separates as soon from the globule, as thirty seconds 

 after the blood has issued from the vein. They, however, agree with him in saying, 

 that these central spheres (the smaller globules) unite themselves in filaments, which 

 differ in no respect from the muscular fibre. They observed also small globules in the 

 milk, in pus, and in the chyle ; and they consider "that those of the former fluids have 

 been, and these of the latter are to be, surrounded by the colouring matter of the 

 blood. 



Messrs. Prevost and Dumas found the globules of the blood to be circular in all the 

 mammalia ; and in their size to vary in different animals ; they are. smallest in the goat. 



The globules are elliptical in birds, and they vary considerably in size in this class of 

 animals. This variation is chiefly in the great axis of the globules. They are ellip- 

 tical also in all cold-blooded animals. 



IF. Of the. Coagulation of the Blood, On this part of the subject before us, we cannot 

 enter minutely. We will merely state, as briefly as we can, those inferences at which 

 we have arrived, after a careful "examination of the phenomenon itself, under various 

 circumstances, and of the different opinions entertained respecting it. 



1. According to the observations of Treviranus and Kolk, whose observations on this 

 subject have been extended and faithful, the particles or globules of the blood possess 

 a rotatory motion during life, and this motion continues until the phenomenon of coa- 

 gulation takes place. 



2. That this motion of the globules is the cause of the blood's fluidity. 



3. That the motion of the globules is the consequence of the vital influence emanat- 

 ing from the glanglial nerves distributed in the parietesof the vessels in which they cir- 

 culate. 



4. That the cause of the coagulation of the blood is not to be found in external agen- 

 cies but in the loss of that emanation, (proceeding from the organic nerves distributed 

 to the coats of the vessels,) of the vital influence with which the globules are en- 

 dowed. 



5. That the presence of the air, especially of the oxygenous portion of it, promotes 

 this phenomenon. 



6. That when coagulation commences at any point of a mass of blood it is rapidly 

 propagated throughout the whole ; this may arise from the cause being co-ordinate, or 

 nearly so, throughout the whole. 



second. It manifests also a great disposition to form aggregates or ranges, in the form 

 of a string of beads. 



The coloured portion appears to be a kind of jelly, easily divisible, but insoluble in 

 water, from which it may always be separated by repose/ It is likewise transparent, 

 but much less so than the central corpuscle ; and the fragments arising from its division 

 are not susceptible of regular aggregation. As the attraction, which keeps the red 

 substance fixed round the white globules, ceases at the same time with the movement 

 of the liquid, these globules can then obey the force whvh tends to unite them, and to 

 form a net-work, in whose meshes the liberated red colouring matter gets enclosed ; 

 and thus produce the phenomenon of coagulation. If the eoagultim be exposed to 

 a stream (jf water, the colouring matter is washed away, while the aggregate formed 

 by the white globules remains in the form of filaments, in which may be recognised, by 

 means of the microscope, the aspect and structure of the muscular fibre. 



Three animal substances ought, therefore, to fix our attention : these are, the albu- 

 men of the blood, the white globule, and the colouring matter which envelopes this. 

 With respect to the colouring particles of the blood, these chemists suppose that it. is 

 formed of an animal substance, in combination with a peroxide of iron. The colourless 

 globules they consider to be coagulated allnimcn. They have examined the proportion 

 which the white corpuscles and red matter together bear to the rest of the blood, in a 

 great variety of animals ; and they find them most abundant in birds, next in the mamma- 

 lia, especially the carnivorous mammalia ; and they are least plentiful in cold-blooded 

 animals. In man they consftute about one hundred and twenty -nine parts by weight, 

 per thousand. They are iiiore abundant in arterial than in venous blood ; one thousand 

 parts of the arterial blood of the sheep, dog, and cat, contain ten parts more of these 

 particles than blood taken from the veins. The serum is identical in both. 



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