viii SUPPOSED SPONTANEOUS COAGULATION 323 



Altmann had previously arrived at in connection with the staining 

 of the unsatisfied oleic acid. 1 



11. 'Spontaneous' Coagulation of Albumins (seep. 266) 



According to Cohnheim, certain albumins, for example, fibrinogen, 

 casein, some cell-plasms, and perhaps also para-myosinogen and 

 myosinogen, may assume ' spontaneously ' a peculiar state which is 

 intermediate between the originally soluble and the ultimately 

 precipitated condition. These albumins are chemically altered and 

 precipitated under the influence of certain ferments, but are then still 

 relatively soluble, and may be precipitated still further and become 

 denaturalised by such agencies as heat, formaldehyde, alcohol, and 

 other means. For this second 'coagulation,' a second 'heat-coagula- 

 tion-temperature ' exists, which can be determined at least for fibrin, 

 and which differs from that of the original fibrinogen (see, however, 

 p. 378). Cohnheim thinks it is necessary, therefore, to distinguish, as 

 Arthus 2 has done recently, several distinct processes, namely : 



(1) Precipitation or precipitation without denaturalisation by 



means of salting out or by acidification. 



(2) Caseification or solidification which is induced by ferments, as, 



for example, when rennet acts on caseinogen. 



(3) Coagulation or denaturalisation which destroys the colloidal 



character of the albumin. 



The author does not agree with Cohnheim in this view; the 

 classification of Arthus is a very artificial one, for under 'precipita- 

 tion' are classed the two entirely different processes of (1) rendering a 

 compound supersaturated by the withdrawal of water as in the case 

 of salting out, and (2) causing neutralisation precipitates by the addition 

 of acids. Under ' caseification ' we must remember that salts are 

 absolutely necessary in addition to the albumins and the ferments, 

 and ' coagulation ' need by no means destroy the colloidal character 

 of albumins, as is well seen in the case of globulin prepared by 

 Starke's method, 3 namely, by diluting egg- white with ten times its 

 bulk of water (see p. 322), and then dialysing the solution at a 

 temperature of 75-85 C. The globulin formed by this process is 

 insoluble in pure water and in neutral salt solutions, but passes into 

 solution on being treated with very dilute alkalies or with dilute 

 acids (Mann). 4 When in solution, the globulin, formed out of egg- 



1 Mann, Physiological Histology, 1902, p. 306. 



2 M. Arthus, Arch, de Physiologic norm, et pathol. 1893, p. 673. 



3 J. Starke, Zdt.f. Biol 4O. 419, 494. 



4 Mann, Physiological Histology, 1902, p. 58. 



