4 DESCRIPTION OF THE BLOOD. 



capable of enlargement according to the amount of liquid which they are called upon 

 to hold. In some animals, such as the cow, these reservoirs are extremely large, being 

 capable of containing at least a quart of milk. The reservoirs are much smaller towards 

 the mamma itself, and serve as tubes for the conveyance of the milk into the mouth 

 of the young. Of the milk itself we shall speak in another part of the work. 



The BLOOD of the Vertebrate animals is of a light red color when freshly drawn 

 from the arteries. This wondrous fluid, in which is hidden the life principle that 

 animates the being, is of a most complex structure, as may be imagined when it is 

 remembered that all the parts of the body are formed from the blood ; and there- 

 fore to give a full description of that fluid would occupy more space than can be 

 afforded to one subject. It is, however, so important a substance that it demands some 

 notice. 



When it is freshly drawn, the blood appears to be of an uniform consistence, but if 

 poured info a vessel and suffered to remain undisturbed it soon begins to change its 

 aspect. A comparatively solid and curd-like mass, of a deep red color, rises to the 

 surface, and there forms a kind of cake, while the liquid on which it floats is limpid and 

 almost colorless. The solid mass is called the clot, and the liquid is known by the 

 name of serum. The whole time consumed in this curious process is about twenty 

 minutes. While thus coagulating the blood gives out a peculiar odor, which, although 

 far from powerful, can be perceived at some distance, and to many persons is inex- 

 pressibly revolting. 



The upper part of the clot is covered with a thick film of an elastic and tenacious 

 nature, which can be washed free from the red coloring substance, and then appears of 

 a yellowish white tint. It can be drawn out and spread between the fingers, as if it 

 were an organic membrane ; and, as its particles arrange themselves into fibres, the 

 substance is called fibrin. When a portion of fibrin is drawn out until it is much 

 lengthened, the fibres are seen crossing each other in all directions, sometimes forming 

 themselves into regular lines. 



The red mass, which remains after the fibrin and serum have been removed, is almost 

 wholly composed of myriads of small rounded bodies, called corpuscules, which can be 

 readily seen by spreading a drop of blood very thinly on glass, and examining it with a 



microscope. The general appearance of the blood corpuscules 

 of man is seen in the accompanying illustration. Some of the 

 disk-like corpuscules are seen scattered about, while others 

 have run together and adhered 'by their flat sides, until they 

 look somewhat like rouleaux of coin. There is sufficient dis- 

 tinction between the blood corpuscules of the various Mammalia 

 to indicate to a practised eye the kind of animal from which 

 they were taken ; while the blood of the four great divisions of 

 the Vertebrates is so strongly marked, that a casual glance 

 will detect the ownership of the object under the microscope. 

 The specimen represented above is magnified about two hun- 

 dred diameters. The blood corpuscules of the Mammalia 

 are circular, while those of the other three divisions are more or less elliptical. 



That the blood contains within itself the various substances of which the body is 

 composed, is evident to the intellect, although as yet no investigator has discovered 

 the mode of its operation. 



How the blood corpuscules are generated from the vegetable and animal substances 

 taken into the stomach, we know not ; but we do know that each globule possesses life, 

 passing through its regular stages of birth, development, age, and death. When yet in their 

 first stages of existence, the blood corpuscules are colorless, not taking the well-known 

 ruddy tint until they have attained their full development. The living current that passes 

 through our bodies is truly a fathomless ocean of wonders ! Even the material formation 

 of this fluid is beyond our present sight, which cannot penetrate through the veil which 

 conceals its mysteries. Much less can we explain the connection of the blood with the 

 mind, or know how it is that one thought will send the blood coursing through the frame 



BLOOD CORPUSCLE OF MAN. 



