"372 RETROGRESSIVE CHANGES 



causes death has not been determined, but, as has been before 

 suggested, it seems probable that it is because cataboUc processes are 

 no longer balanced by anabolic processes, and with these latter oxi- 

 dizing enzymes seem to be inseparab'y associated as far as our pres- 

 ent knowledge shows us. That the loss of oxygen alone, with other 

 materials presumably supplied to the cells in adequate amount, may 

 cause necrosis, is shown by the presence of marked hepatic necrosis 

 in animals kept a week in atmospheres extremely low in oxygen (5-9 

 per cent.)-^^ The nature of the chemical changes taking place in a 

 cell when oxj^gen is deficient must be very different from the normal 

 changes, and hence abnormal toxic substances may accumulate, e. g., 

 excessive amounts of organic acids. Were it not that the proteolytic 

 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 

 connection 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 me+azoa the 

 maximum temperature 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. Kiihne, 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 exactly 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 immediatel}'' fatal to mammals (47°) is exactly the same as 

 the coagulating temperature of the lowest coagulating protein of 



19 Martin, Loevenhart and Bunting, Jour. Exp. Med., 191S (27), 399. 



^"Literature, see Davenport, "Experimental Morphology," New York, 1S97; 

 Schmaus and Albrecht, Ergebnisse dcr Pathol., 1890 (."3, Abt. 1), 470. 



^' Tlie adaptation of animal cells to high tcniperaturos i.s an interesting topic, 

 especially in view of such results as those of Dallingor, who, by raising the tem- 

 perature gradually during several years, caused flagollatn, with a normal maxinuuu 

 of about 21° -23° to become capable of living at 70° (see Davenpotr.). 



" "Biochemistry of Muscle and Nerve," Phila., 1904. 



2^ Quoted by Halliburton. 



