Dr. Buchanan cm the Fibrin contained in the Animal Fluids, 143 



granules, vesicles, and filaments are gradually developed in it. I shall 

 now endeavour to show that a liquid similarly constituted probably 

 exists in all parts of the body, and is therefore to be regarded as the 

 cyto-blastema, or plastic liquid, which gives origin to the cell-germs 

 and cells, out of which all the tissues of the body are developed. 



5. Origin of^ in cavities of body. — The liquid in which the fibrinous 

 corpuscles have been observed to originate, is a mixture of the serum 

 of the blood with the serum of the serous cavities. The latter differs 

 from the former in chemical composition and qualities.* It consists, 

 most probably, of the serum of the blood, effused from the capillary 

 blood vessels into the interstitial cells of the serous tissue, and there 

 modified by serving for the nutrition of the serous membranes. Now 

 the serous membranes have a basis of gelatin, and are, therefore, 

 similar in constitution to the great majority of the tissues of the body. 

 In all the gelatinous tissues, therefore, the process of nutrition must 

 produce a similar modification of tlie serum of the blood ; and we shall 

 thus have all over the body a liquid produced analogous to the serum 

 of the serous cavities. If, then, the serum of the blood is only effused 

 in the quantity necessary for the purpose of nutrition, it will all 

 undergo the same change, and the modified serous liquid will be 

 absorbed by the blood vessels and lymphatics, to make way for the 

 portion next to be effused. When, however, as in early life, the serum 

 of the blood is poured out in greater abundance than is necessary for 

 the nutritive actions, the excess of it will mingle with the modified 

 liquid in the cavities ; and just as in the artificial mixture of these 

 liquids, we shall have a development of cell-germs and cells. Hence 

 the activity of development in early life, and why it keeps pace with 

 the activity of digestion and sanguification ; and, as these functions 

 become less active, declines in the same proportion. Hence also the 

 reason why it continues constantly in an active state on the surface of 

 the skin, forming the cells which flatten into the scales of the epidermis, 

 because the effused serum is here always in excess, being only upon 

 one side in contact with a tissue capable of acting upon it, and modi< 

 fying its composition. Hence also the renewed activity of this func- 

 tion on the occurrence of inflammation, when the increased afflux of 

 blood causes a copious effusion of serum into the cells of the inflamed 

 tissue. 



6. Origin of, in vessels : in healthy state, only in lymphatics. — The 

 same actions which go on in the shut cavities of the body, go on also in 

 the vessels. These having a basis of gelatin, modify the serum effused, 

 for the purposes of nutrition, into the substance of their parietes, and 

 have thence a supply of the modified liquid poured into their interior ; 

 but a much more abundant supply is provided for them by the absorp- 



* Dr. R. D. Thomson. 



