1566 
Two cats were locked up each in a hutch, while another was 
free to move about in the same room. After some time an estimation 
was performed for each of them of the content of kreatin in the 
left and the right M. triceps brachii. 
The determinations were conducted as described above. 
The result was as follows: 
I free to move about for a week, Left 3.400, Right 3.460 
Il locked up for two weeks, A eye; 4° soa 
It (5 peen streem; 0 en BSA 
The values are expressed in mgrms. kreatinin per 1 grm. muscle. 
They tally satisfactorily with the average amount found in cats 
examined before. The quantity of kreatin in the muscles had not 
decreased after the animals had been confined to a narrow space 
for a couple of weeks. 
This however did not disprove our hypothesis conclusively. One 
factor had been left out of calculation, which might perhaps be of 
prime importance, viz. the temperature of the surroundings of the 
cat. The cat first examined, whose left foreleg had been deprived 
of tonus, had been living in the hutch in the first half of September. 
The huteh had been deposited in a partition of the basement of the 
laboratory, of which the window was shut during the night, but 
was kept open all day. The temperature, therefore, did not differ 
much from that of the outside air. The second experiment, that 
upon the normal cats, was carried out in October, when the air was 
rather cooler. The readings, of the Meteorglogical Institute at De Bilt, 
recorded the mean temperature of 15°.5 C. (max. 19°.5 — min. 9° C.) 
from 1—20 Sept. 1915, whereas that of October was 8° C. (max. 
12° — min. 4° C.). Now it is well-known, and it has been proved 
by Prrücer’s extensive researches upon animals, that, as soon as 
there is any danger of cooling, the organism of homoiothermic 
animals is apt to make up for the fall of body-temperature by a 
corresponding rise of heat-production, as effected involuntarily by a 
higher metabolism in the muscles. Since visible movements, alternate 
contraction of various muscles, need not come into play here at all, 
it is not altogether improbable that an exalted muscular tonicity has 
something to do with it. We now had to ascertain whether the 
amount of kreatin in the muscles keeps constant, if not only the 
animal is limited in its movements, but also the heat production 
is not exalted by the surroundings. 
The experiment was, therefore, repeated. The room was heated 
by means of a gas-stove and adequately ventilated through an open 
window the whole day. 
