16 MANUAL OF HISTOLOGY. 



superoxide of hydrogen is rapidly decomposed by fibrin. Fibrin may be 

 obtained from blood, chyle, and lymph, in small but variable quantity, 

 also from serous transudations. 



Let us now consider for a few moments the phenomena of coagulation 

 of fibrin. Fluids in which this substance is contained become of a 

 thickish or even jelly-like consistence soon after coming to a state of 

 rest. Later, in consequence of progressive contraction of the fibrin, a 

 certain quantity of the entangled fluid is squeezed out, and the coagu- 

 lum becomes more or less solid as it decreases gradually in size. Under 

 the microscope a homogeneous jelly is at first perceived ; later on a tangle 

 of usually very delicate threads or fibres (rarely broad), by which the 

 cellular corpuscles of the fluid are caught. By many these fibres are re- 

 garded as the optical expression of folds or rugae on fine membranous masses. 



In regard to the origin of fibrin, it was for a long time generally sup- 

 posed that it took its rise from albumen. And from the fact that its 

 analysis showed a larger proportion of oxygen than is found in the latter, 

 the hypothesis was advanced that fibrin is formed by a process of oxida- 

 tion or putrefaction from albuminous substances. 



Some years ago an interesting discovery was published by A. Schmidt, 

 which completely upset all earlier theories as to the constitution of the 

 material in question. 



According to this observer, there exists no fluid fibrin at all in the 

 animal fluids as long as in motion. It is first generated in the blood and 

 other liquids by the chemical combination of two nearly related com-, 

 pounds, which have been named by the author "fbrinogen" and " fibrino- 

 plastin" The first of these (also called metaglobulin) is dissolved in the 

 plasma of the blood; the second (or paraglobulin), which, combining 

 with fibrinogen, converts it into fibrin, exists, on the contrary, according 

 to Schmidt, in the bodies of the coloured blood-cells, passing from these 

 into the plasma. It is exceedingly similar to the globulin of these cells, 

 ( 12), or perhaps identical, and probably corresponded with the so- 

 called "serum casein," (A. Schmidf). Lymph, chyle, pus, and many 

 tissues containing cells (but not cartilage and tendon), and also fluids 

 into which these cell-contents have passed, as, for instance, the serum of 

 the blood, synovia, humours of the eye, and saliva, are all fibrinoplastic. 

 Fibrinogen also, which is very like fibrinoplastin in its reactions both 

 may be precipitated from dilute solutions by conducting through them a 

 stream of carbonic acid appears widely distributed throughout the sys- 

 tem, and is contained in almost all serous fluids, as well as those saturat- 

 ing connective tissue and muscle. The rapid mutation of matter which 

 takes place in the moving juices of the -body is supposed to be the 

 obstacle to the formation of fibrin during life. Schmidt believes himself 

 also justified in the conclusion that, on the chemical combination of these 

 two " mother substances " to form coagulated fibrin, the alkalies, which 

 previously held them in solution, are set free. 



12. 

 Myosin. Muscle-Fibrin, or Syntonin. 



The contractile structures of the organism, the protoplasm of which 

 the bodies of young cells are formed, with striped and smooth muscle- 

 fibres, all consist of a series of albuminous substances remarkable for 



