1. Rat sarcoma may be cultivated in mouse plasma and guinea pig plasma, and the growth differs only in extent from that observed in rat plasma. The cells may show active wandering in guinea pig plasma after thirty days, if transferred at proper intervals to fresh medium.

2. Rabbit plasma is less suitable than that of guinea pigs and mice for the growth of rat sarcoma; growth is slow, but it may continue for twelve days.

3. The duration of growth of rat sarcoma in dog plasma is from two to three days.

4. The duration of the growth of rat sarcoma in pigeon plasma is four to five days. Transferring the tissue to fresh pigeon plasma does not lengthen the period of activity.

5. No growth whatever is observed of mouse and rat tissues in goat plasma. Studies of the fate of the cells indicate the presence in goat serum of a substance toxic for these tissues.

6. In preparations of rat sarcoma in human plasma, liquefaction of fibrin is regularly observed. The phenomena of growth consist in an outwandering of cells along the cover glass, and, after four to six days, the formation of giant cells. Such giant cells are produced in larger number in the cultivation of rat spleen.

7. The degree of suitability of the different kinds of alien plasma used as culture media for mouse and rat tissues does not go hand in hand with the closeness of relationship of the species.

8. Rat spleen may be cultivated as readily in foreign plasma as the virulent transplantable tumors.

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