474 Journal of Agricultural Research voi. xv, no. s 



bator at 40° C, in a refrigerator at 10° C, and at room temperature. 

 At the end of about three hours each watch glass was examined and the 

 following results noted: The larvae from the refrigerator were rigid 

 though not tightly coiled. After standing at room temperature for sev- 

 eral minutes they became active, but no evidence of molting could be 

 found. A careful examination of the contents of the watch glass failed 

 to show any cast-off cuticles. The larvae which had been left at room 

 temperature were in the act of molting, but with the possible exception 

 of two or three, the process had not been completed. The larvae from 

 the incubator were feverishly active and nearly all of them had com- 

 pletely cast off their cuticles, which were found at the bottom of the 

 dish. Some were in the act of molting again. 



Thus it is evident that temperature is a prime factor in the growth of 

 the intestinal trichinae. It is rather significant that a temperature of 

 10° C, inhibited the growth process without exerting a deleterious effect 

 on the larvae. In fact, after removal to room temperature one of the 

 larvae which had been kept in the refrigerator was seen to commence to 

 molt, but as the observation was not continued it is not known whether 

 the process was completed. The life processes of Trichinella spiralis 

 under experimental conditions are modifiable to a considerable extent 

 by certain environmental factors. Within certain limits they may be 

 retarded by low temperatures and accelerated by high temperatures 

 after the parasites are taken out of their host. 



In the above experiment it was noted that certain larvae behaved 

 quite differently from the others. At room temperature as well as in the 

 incubator they remained tightly coiled. The parasites in the dish taken 

 from the incubator were all active at first, but at the end of about 30 

 minutes a number of larvae became sluggish and finally coiled up. The 

 assumption was made that the coiled larvae were still intact so far as 

 further growth was concerned and that they had apparently remained 

 uninfluenced by their stay in the intestine. It was obvious that the 

 incubator temperature did not stimulate them to development, but in 

 order to settle this point more definitely the following experiment was 

 performed. 



A rat was killed within 20 hours after feeding trichinous meat. The 

 larvae after being isolated from the intestine were allowed to remain at 

 room temperature for about an hour and only those which became tightly 

 coiled were isolated and placed in another watch glass. The latter was 

 kept under observation for about 30 minutes, and those larvae which 

 were not definitely coiled were taken out by means of a pipette. The 

 dish was then covered and placed in an incubator at 40° C. for three 

 hours. When the parasites were removed to room temperature they 

 were quite active. Gradually their activities ceased, and they began to 

 coil up. No cast-off cuticles were found in the dish and no parasites 

 were seen to be molting. 



