498 THE BLOOD. 



The Cnista inflammatoria or buffy coat, a yellowish- 

 white, semi-solid, membranous mass, which is some- 

 times formed on blood let from the vein, is produced 

 by the sinking of the blood-corpuscles to a certain ex- 

 tent before the coagulation of the fibrin, the upper 

 layer of the solution thus coagulating without inclosing 

 blood-corpuscles. It is produced under the most varied 

 conditions, particularly when the specific gravity of 

 the serum of the blood is lowered, so that the cor- 

 puscles can sink more rapidly, as, for example, after 

 frequent letting of blood. It is almost always formed 

 in the blood of certain animals, as, for instance, the 

 horse, in which the corpuscles possess the property of 

 sinking readily. It was formerly incorrectly considered 

 as a sign of inflammation. 



Many variations in the composition of the blood 

 have been observed in diseased conditions of the body. 

 In diabetes for instance, it contains sugar, which more- 

 over is said to be contained in normal blood, though in 

 exceedingly small quantity. 



Respiration. The dark venous blood, mixed with, 

 the chyle of the thoracic duct, is poured into the right 

 auricle of the hearlf, through the two grand trunks of 

 the venous system, the venae cavse; from the auricle if, 

 passes into the corresponding ventricle, and from this 

 is projected into the lungs'. It is returned from the 

 latter to the left auricle as bright-red arterial blood ; 

 passes into the left ventricle from which it is thrown 

 into the whole body by means of the principal artery, 

 the aorta. The lungs consist of the fine, terminal, 

 vesicular branches of the bronchial tubes, on the walls 

 of which exceedingly fine networks of capillary blood- 

 vessels are spread out. The inspired air is brought in 

 contact with the venous blood, through the fine walls 

 of these air cells, which are impregnated with water; 

 4-5 per cent, of the volume of the air being absorbed 

 as oxygen, and a volume of carbonic acid, together 

 with some nitrogen, almost equal to that of the ab- 

 sorbed air, being given off, and in the expiration 

 removed from the body, together with a large amount 

 of water vapor. This carbonic acid is formed in the 



