372 RETROGRESSIVE CHANGES 



enzymes continue in action after nutrition is shut off, the cells might 

 remain in a completely unaltered condition for an indefinite period, 

 and capable of resuming- their function when nourishment is again 

 supplied, which is decidedly contrary to the facts. (The general 

 features of anemic necrosis have been already discussed in the pre- 

 ceding paragraphs, and also under the subject of infarction.) 



Thermic Alterations. — These have been studied particularly in 

 conneetion with the cells of the lower organisms.^^ While some uni- 

 cellular organisms can survive a temperature of 69°, most of them 

 are killed at from 40°-45°. For the great majority of metazoa the 

 nicfximum temi)erature lies below 45°, and in the case of marine 

 species below 40°." The heating is accompanied by the appearance 

 of granules in the cytoplasm, which become larger until the condi- 

 tion of "heat rigor" sets in. Kiihue, in 1864, showed that in muscle 

 cells, at least, there is contained a protein which becomes turbid 

 through partial coagulation at 40°, and Halliburton ^^ has found 

 that in nearly all tissues are globulins coagulating at from 45°-50° ; 

 it is probable, therefore, that the granules formed in heated cells are 

 produced through coagulation of these proteins. The importance of 

 this coagulation in determining death is not yet fully established, 

 but it would seem to be very great. Halliburton has observed that 

 in both muscles and nerves to which heat is applied, contractions 

 occur at various temperatures, corresponding exactlj^ with the tem- 

 peratures at which the several varieties of the proteins of the cells 

 coagulate. Furthermore, Mott ^"^ has found that the temperature 

 that is immediately fatal to mammals (47°) is exactly the same as 

 the coagulating temperature of the lowest coagulating protein of 

 nerve-cells. This fact is undoubtedly of great practical importance 

 in causing death from fever, for although 47° C. (117° F.) is prob- 

 ably never reached in man, yet application of much lower tempera- 

 tures, even 42° (108° F.), for a few hours will cause coagulation 

 of these proteins (all proteins coagulate at less than their ordinary 

 coagulation point if the heating is continued for a long time). It 

 would seem from the above observation that heat may cause cell death 

 through coagulation of the proteins. AVhethei- the cell death is in 

 any way dependent upon destruction of the enzymes by heat has not 

 been ascertained ; but as most enzymes are not destroyed much be- 

 low 60°-70°, it seems improbable that they are greatly injured at 

 the temperatures at which cells are killed. It is possible, however, 

 that under the conditions in which enzymes exist in the cell they 



i- Literature, see Davenport, "Experimental Aforphology," New 'Sork, 1S!)7; 

 Schmaus and Albrecht, Erpebnisse der Pathol.. 1896 (,1, Abt. 1), 470. 



14 The adaptation of animal cells to hipli temperatures is an interosliiii,^ topic, 

 especially in view of sueli results as tliose of Daliinfjer, wiio, by raisiui: tlie teni- 

 peraturo gradually durin<j several years, caused llaffeliata witli a normal maxiiiniiu 

 of about 21°-2.'i° to become capable of livinp at 70° (see Davenport). 



in "Biochemistry of Muscle and Nerve," rhila.. 1004. 



10 Quoted by irallilturlon. 



