106 Scientific Proceedings (49). 



that in some cases 60 to 100 per cent, of the eggs of egg masses 

 kept in a depth of 12 to 18 inches of quiet, poorly oxygenated 

 water died, while in similar adjoining vessels eggs less than half 

 submerged developed almost without exception. 



76 (685) 



Direct observation of cell division in mammalian tissue. 



By ROBERT A. LAMBERT. 



[From the Department of Pathology, College of Physicians and 

 Surgeons, Columbia University.] 



Connective tissue cells of the rat cultivated outside the body 

 in rat plasma for as long as seventy-six days formed the material 

 for observation. For maintaining activity for such a period, the 

 pieces of tissue were transferred to fresh plasma at intervals of 

 five to ten days. Measures employed by Carrel for rejuvenating 

 the cells in old cultures were found to be unnecessary. 



We have found that the process of karyokinetic division may 

 be followed in the living cells. The earlier phases often escape 

 notice. The later phases, however, may be observed with ease 

 even with the lower powers of the microscope. In actively 

 growing cultures the time required for the entire process is from 

 forty to sixty minutes. The time elapsing between the divergence 

 of the masses of daughter chromosomes to complete division of the 

 cytoplasm averages about ten minutes. In slowly growing cul- 

 tures the process may be retarded. A half hour to an hour after 

 division is required for the daughter cells to develop the form and 

 staining qualities of the resting cell. These time periods relate to 

 observations made on cells at 35-37°C. At lower temperatures 

 (25-30 0 ) the process is slower. 



Cells containing numerous fat droplets have been seen to 

 divide as rapidly as cells free from fat. 



Amitotic division has not been observed. 



Cells after division have been followed and further division 

 noted. The size reached by these daughter cells was approxi- 

 mately that of the parent cells. This observation affords proof 

 that true growth takes place in cells cultivated in vitro. 



