ON THE RESPIRATION OF CHELONIA. 519 
PLatEe 33. (IV.) 
Fig. 1. View of right half of brain, from outside. 
Fig. 2. View of the left half, from the inside. 
Fig. 3. View of left half, from the outside. 
ss. Suprasylvian fissure, 
ssa. Its anterior limb. 
sss. Superior limb. 
ssp. Posterior limb. 
ssd. Descending limb. 
84. NOTE ON THE MECHANISM OF RESPIRATION AS 
WELL AS OF THE RETRACTION OF THE HEAD 
AND LIMBS IN CERTAIN CHELONIA.* 
For some time past I have been acquainted with the fact that in page gag, 
Tortoises the movement of the limbs influences the degree of inflation 
of the lungs; and on one occasion I have been able, in a dead speci- 
men ofa large species, to blow out a candle by means of the current 
of air issuing from the nostrils consequent upon my forcibly pushing 
~ inwards one of the previously extended anterior limbs. From this I 
inferred that the rigidity of the thoracic and abdominal walls (which 
entirely precludes their being employed in respiration) is made up for 
by the great difference in the capacity of the thoracic and abdominal Page 650. 
cavities which results from differences in the degree of retraction of 
the limbs. And I also inferred that the activity of the respiratory - 
moyements—as in the Lobster, which has some of its larger gills con- 
nected with the bases of the ambulacral legs—must depend, in great 
measure, on the amount of the mechanical force employed in locomo- 
tion, in the same way that in the locomotive steam-engine the draught 
through the boiler-tubes of the furnace depends upon the rapidity of 
the movement of the engine, because the waste-steam pipe is made to 
open at the bottom of the funnel. 
A specimen of Trionyx perocellatus (three and a half inches in 
length of carapace), which had died a day or two previously, lying on 
my dissecting-room table with its neck and limbs fully extended, I 
happened to take it up by the lateral margins of its shell, when, upon 
grasping it between my fingers and thumb, I noticed, to my surprise, 
that its head and limbs immediately retracted to their full extent. At 
; 
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* “Proceedings of the Zoological Society,” 1879, pp. 649-50. Read, June 17, 
1879. 
