GENERAL ANATOMY. 



fluids of the body, which are intended for its nutrition, are the lymph, 

 _L the chyle, and the blood. There are other fluids also which partially 

 subserve the same purpose, as the saliva, the gastric juice, the bile, the intestinal 

 secretion ; and others which are purely excrementitious, as the urine. But there 

 is no need to describe the rest in this place, since they are the secretions of special 

 organs, and are described, as far as is judged necessary for the purposes of this 

 work, in subsequent pages. We shall here speak first of the blood, and next of 

 the lymph and chyle. 



THE BLOOD. 



The blood is a thickish, opaque fluid, of a bright-red or scarlet color when it 

 flows from the arteries, of a dark-red or purple color when it flows from the veins. 

 It is viscid, and has a somewhat clammy feeling ; it is salt to the taste, and has a 

 peculiar faint odor. It has an alkaline reaction. Its specific gravity at 60 F. is 

 about 1.0.3.5. and its temperature is generally about 100 F., though varying 

 slightly in different parts of the body. 



General Composition of the Blood. When blood is drawn from the body and 

 allowed to stand, it solidifies in the course of a very few minutes into a jelly-like 

 mass, which has the same appearance and volume as the fluid blood, and, like it, 

 looks quite uniform. Soon, however, drops of a transparent yellowish fluid begin 

 to ooze out from the surface of this mass and to collect around it. Coincidently 

 with this the clot begins to contract, so that, in the course of about twenty-four 

 hours, the original mass of coagulated blood has become sepai-ated into two parts 

 a ; 'clot " or "coagulum," considerably smaller and firmer than the first-formed 

 jelly-like mass, and a large quantitv of yellowish fluid, the serum, 'in which the 

 clot floats. 



The clot thus formed consists of a solid, colorless material, called fibrin, and 

 a large number of minute cells or corpuscles, called blood-corpuscles, which are 

 entangled and enclosed in the fibrin. The fibrin is formed during the act of solidi- 

 fication. In the fluid blood in the living body there is a substance, named 

 fibrinogen, which when acted upon by a second material, also contained in the 

 blood, and named a fibrin-ferment, forms a solid substance, fibrin. This latter 

 in its process of solidification encloses and entangles the blood-corpuscles, and 

 thus the clot is formed. 



Recent observations have shown that the presence of a trace of a calcium salt 

 is a necessary condition for the transformation of fibrinogen into fibrin. The 

 fibrin-ferment does not exist as such in the blood contained in the blood-vessels, 

 but seems to result from the destruction of what are known as the white corpus- 

 cles and the blood-plaques to be described later. These structures, more espe- 

 cially the plaques, disintegrate very rapidly when blood is drawn from the body, 

 liberating the ferment, and so producing coagulation, and lesions of the cells 

 lining the interior of the blood-vessels seem also to give rise to ferment-produc- 

 tion and the intra-vascular formation of fibrin. 



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