1,92. QUARTERLY JOURNAL. 



neys ; and 3d, the elements of bile, which contains a large propor- 

 tion of carbon united with hydrogen, and which after answering 

 a particular purpose in digestion, is re-absorbed with the food, and 

 finally rejected in the form of carbonic acid and water. 



To complete this account of the excretions, it is only neces- 

 sary to add, that the saline ingredients of the blood are also thrown 

 off by the kidneys. 



We now pass to the examination • . those constituents of the 

 blood which serve for the composition of . tissues. 



The fibrin of the blood is the nutritive atter out of which the 

 tissues are formed. This substance, whi' is in a state of solution.^ 

 while circulating in the vessels, becomes ffused through the walls* 

 of the capillary vessels, and thr is bro'ight in direct contact w'thd 

 the organized tissues. Here cfc/lain changes occur in it ; first, i^l 

 assumes a granular appearance, these granules aggregate togeth 

 to form nuclei, and around th( e nuclei membranes form by whic 

 they are converted into cells. These cells, constitute the primi- 

 tive condition of all organized tissues, and by various transforma-J 

 tions are converted into the particular tissue in the midst of whic! 

 they are formed. All the organs are then formed from the fibril 

 of the blood, and in proportion as a particle is removed by the a 

 of decomposition to which I have alluded, it is replaced from thi 

 fibrin circulating through the capillary vessels. Whence is th; 

 fibrin of the blood derived ? and how is the constant supply ke 

 up? 



The albumen dissolved in the serum is the ingredient out of 

 which the fibrin is formed ; it is the shape which nutritive matter 

 assumes before it becomes fibrin. The similarity of composition 

 between albumen and fibrin has been already pointed out, but 

 there is a further difference of which their chemical constitution 

 gives no explanation. Fibrin coagulates, has a tendency to be- 

 come organized ; it is albumen more highly elaborated and vitaliz- 

 ed. The conversion of albumen into fibrin takes place in the 

 blood by means of colorless cells, which differ from the red disks 

 both in their structure and properties. I have already briefly allu- 

 ded to them. 



The saline ingredients of the blood enter into the composition 

 of some parts, as the bones, and also seem to have other uses 

 vithich are not yet well understood. 



