December 4, 1914] 



SCIENCE 



825 



and of the cockroach, Periplaneta Americana. 

 The follicles of the testis are isolated under 

 the dissecting microscope and, on tearing the 

 follicular envelope, the cells are set free. A 

 good medium appears to be diluted Ringer's 

 fluid to which has been added a trace of egg 

 albumin. For the cells of the cockroach I 

 used the body fluid collected by means of a 

 capillary pipette. As the cells are very sus- 

 ceptible to mechanical stimulation care is 

 necessary in these preliminary manipulations. 



An uninjured, normal, isolated spermatocyte 

 when not in division assumes a spherical 

 shape. The nucleus occupies the center of the 

 cell and, during the growth period, appears 

 almost perfectly hyaline. In Disosteira three 

 bodies stand out in the nucleus, their indices 

 of refraction being different from that of the 

 surrounding medium. One of them is rather 

 elongated and lies immediately under the 

 nuclear membrane. The other two are more 

 or less globular and frequently lie well within 

 the substance of the nucleus. In the cock- 

 roach only one such body or nucleolus is 

 apparent. 



Occasionally nuclei are met with in which 

 may be discerned a mass of hazy filaments of 

 very ill-defined outlines. It is possible that 

 these are nuclei which have been unduly stimu- 

 lated in teasing the tissue. Other nuclei are 

 also discernible in which hazy bodies, the pro- 

 phase chromosomes, are to be recognized 

 scattered throughout the substance of the 

 nucleus. In cells undergoing division the 

 chromosomes are plainly visible during the 

 meta- and anaphases. 



Injury and frequently mere mechanical 

 agitation of the cell produces a remarkable 

 change in the appearance of the nucleus. 

 The hitherto optically structureless nucleus 

 begins to give evidence of hazy filament of 

 a loose granular aspect. They lie imme- 

 diately under the nuclear membrane and 

 one gains the impression that they are pro- 

 duced by a lineal condensation or precipitation 

 of granules in the hyaline nuclear substance. 

 Within a few minutes the filaments become 

 more distinct and thicken as the granules ap- 

 pear closer together. Free ends are soon to be 



noticed and one may occasionally trace a 

 filament from one end to the other throughout 

 its irregular winding course. They can not, 

 however, be counted because they are hope- 

 lessly entangled. A light line down the middle 

 of the filaments gives them the appearance of 

 being longitudinally split. The granules are 

 collected in bunches all along the length of 

 the filament, giving it a cross striated effect. 

 In those filaments which can be seen on end 

 the granules are found to be arranged more 

 or less regularly about a hyaline core. Such 

 a structure may explain the longitudinally 

 split appearance of the filament when viewed 

 on the side. 



The nuclear substance is a more solid and 

 viscous gel than the cytoplasm. The filaments 

 are still more solid and may be caught in the 

 middle with a needle and drawn out into an 

 attenuated loop fully as long as the diameter 

 of the nucleus. On being set free the fila- 

 ment tends to retract and to thicken again. 

 After the nuclei under observation have 

 reached this stage the filaments collect on one 

 aide of the nucleus, and despite all my at- 

 tempts to prevent it, coalesce into an irregular 

 gelatinous mass. 



The above changes take place in a period 

 of five minutes to half an hour. Tearing of 

 the cytoplasm of the cell accelerates the proc- 

 ess and my conclusion is that the greater the 

 amount of injury the more rapidly do the 

 filaments form. In many cases the tearing 

 causes the cytoplasm to absorb water and to go 

 into solution. In the nuclei of cells so treated 

 the formation of filaments takes place very 

 rapidly. 



The cells may be similarly stimulated by 

 exposure to ether vapor. The nuclear fila- 

 ments and the chromosomes then stand out 

 clearly. Formalin vapor, on the other hand, 

 seems to kill the cells without bringing into 

 evidence the nuclear structure. 



The stimulus produced by injury may be 

 transmitted from the injured cell to a sound 

 one if there be a cytoplasmic connection be- 

 tween the two. This is to be seen on piercing 

 one of the daughter cells in the very late telo- 

 phase of the spermatocyte. Near the end of 



