MICROSCOPIC STRUCTURE OF THE BLOOD. 293 



Fibrinogen. Although it is customary to speak of fibrinogen 

 as if it was a simple substance, yet the fact that when it is dis- 

 solved in salt solution and heated to a temperature between 52 

 C. and 55 C. only a part of the proteid is coagulated, and that 

 when the temperature reaches 65 C. another portion is thrown 

 down, has led Hammarsten to regard it as made up of fibrinogen 

 proper, which coagulates at the lower temperature, and a globulin, 

 fibrin-globulin, which is coagulated at the higher temperature. 

 It is believed that a nucleoproteid is also combined with these two 

 proteids to make up what is commonly termed fibrinogen. 



Origin of Fibrinogen. Matthews, after a very elaborate study 

 of the subject, reported in the American Journal of Physiology, 

 concludes that the decomposing leukocytes of the blood, and 

 chiefly those of the intestinal area, are the sources of the blood 

 fibrinogen, and supports this opinion : u (1) By the increase in the 

 per cent, of fibrinogen in all cases of prolonged leukocytosis 

 accompanying suppuration ; (2) by the increase in fibrinogen 

 during leukocythemia ; (3) by the increase in fibrinogen in pneu- 

 monia, erysipelas, acute rheumatism, peritonitis, and similar in- 

 flammatory conditions ; (4) by the fact that fibrinogen is not 

 simply transformed proteid of the food, as indicated by its con- 

 tinued formation during fasting, and its failure to increase during 

 proteid digestion ; (5) by the observation that neither the spleen, 

 muscles, kidneys, pancreas, nor brain appears to be essential to its 

 formation ; (6) by the well-known fact that there is present in 

 the cell-body of 'the leukocyte a substance which, by the action 

 of a substance coming from the nucleus or arising in its neighbor- 

 hood, is thrown into a fibrillar form closely resembling fibrin- 

 fibrils, and like them contractile ; (7) by the fact that the leuko- 

 cytes are constantly going to pieces in the body, hence must be 

 adding constantly to the proteid constituents of the blood ; (8) by 

 the close correspondence existing between the fibrinogen-content 

 of the blood and the excretion of uric acid ; and (9) by the fact 

 that the intestine, which is rich in leukocytes, appears to be the 

 chief source of the fibrinogen of the body/ 7 



In this article Matthews makes the following statement, which 

 is, to say the least, suggestive, although, of course, as yet not 

 demonstrated : " If fibrinogen is derived from the leukocytes, as the 

 preceding considerations indicate, and if Schmidt's and Morner's 

 observations on paraglobulin indicating its origin in the leukocyte 

 prove well founded, the conclusion would seem obvious that the 

 proteids of the blood are derived from the leukocytes. This 

 would strongly confirm Hoffrneister's view that the leukocytes are 

 pre-eminently active in proteid absorption and assimilation. It 

 would lead to the interesting conclusion that the organism lives on 

 its leukocytes much as the egg-cells of some forms live on their 

 follicle-cells. If this were so, it would explain (1) the true 



