18 Messrs. L. Hill and M. Greenwood, Jun. [Oct. 1, 
If young animals have an advantage here also, it is, to say the least, not 
very marked, and we may reasonably conclude that we have to deal with a 
group in which the absolute body mass of all members is so great that the 
decompression period (four to seven seconds) is too short even for the least 
bulky subjects. 
In addition to this question of absolute body mass, there appear to be quite 
marked variations in different species. Thus, it by no means follows that 
animals of species A will stand decompression better than much heavier 
animals of species B. So far as our observations go, the guinea-pig is a 
peculiarly unfavourable subject, even when young and light animals are used ; 
in 10 experiments we have had eight fatalities. 
12.7.07.—Nine guinea-pigs were exposed to + 105 lbs. for one hour, and 
decompressed in four seconds. Eight (weights, 144, 72, 77, 164:5, 75, 114°5, 
108-5, 81 grammes) were dead, and the ninth (108 grammes) paralysed, but 
recovered completely in a few days. 
We shall next give details of comparative experiments, which suggest the 
same conclusion. 
Rabbits and Cats or Kittens. 
26.7.06.—Four rabbits (about one month old), three kittens (about three 
weeks old) were exposed to + 100 lbs. for 80 minutes, and decompressed in 
seven seconds. Two rabbits died and one kitten. 
21.11.06.—Half-grown cat (3 lbs. 2 ozs.) and large rabbit (3 lbs. 8 ozs.) were 
exposed to + 105 lbs. for 35 minutes. Decompression time, four seconds. 
The cat was dead on removal, the rabbit unaffected. 
Rabbits and Gurinea-prq. oe 
10.5.07.—Two young rabbits (3 lbs. 6 ozs.; 3 lbs. 2 ozs.), one guinea-pig 
(1 lb. 8 ozs.) exposed to + 100 lbs. for 30 minutes, and decompressed in seven 
seconds. 
The rabbits died within 15 minutes, and the guinea-pig died in the night, 
showing signs of pulmonary hemorrhage. 
Rats and Rabbits. 
10.7.07.—Two rats (435 grammes, 87 grammes), one rabbit (1304 grammes) 
exposed to + 105 lbs. for 14 hours, and decompressed in four seconds. 
All were dead on removal. 
Evidently these results are indecisive. 
Rats and Mice. 
7.12.06.—Six rats and six mice were exposed to + 115 lbs. for 25 minutes, 
and decompressed in four seconds. Four rats died (162, 104, 120, 152 
