Henry L. Bruner 107 
In view of Arviset’s objection it seems necessary to admit that the fore- 
going theory fails to furnish a complete explanation of the problem under 
consideration. I wish, therefore, to propose a new theory which has 
been suggested by my studies on the reptiles. These cold-blooded, hiber- 
nating animals certainly do not require a special mechanism to elevate 
the temperature of the inspired air. It is also improbable that the strati- 
fied squamous epithelium of the nasal vestibule permits the escape of any 
considerable amount of moisture, which, moreover, would be readily sup- 
plied by the numerous glands of the nasal cavity. In the lizards and 
snakes the chief function of the spongy tissue of the nasal vestibule is to 
protect the entrance to the true olfactory chamber and lungs, either by 
closing the external naris, so as to exclude foreign bodies, or by facili- 
tating the removal of any obstruction, whether it be the old stratum 
corneum or some foreign object. In the mammals the spongy tissue is 
not used to close the nasal vestibule nor to assist in exuviation, but there 
still remains the possibility that the respiratory passage may be blocked, 
either by secretions from the nasal cavity itself or by foreign matter. 
The removal of such an obstruction is doubtless facilitated by the alter- 
nate swelling and reduction of the spongy body of the inferior turbinate 
region. ‘The origin of such a function is easily explained on the theory 
that the mammals have descended from reptilian ancestors, for if this is 
true, the spongy body has simply retained one of its primitive functions. 
The survival of the spongy body in the nasal vestibule of crocodilians 
is probably to be explained by the exercise of a function similar to that 
just described for the apparently homologous structure in the mammals. 
3. The occurrence of a mechanism for raising the venous blood- 
pressure in the head of reptiles suggests a few words in regard to the 
effect of such pressure on the delicate organs of the head. In the mam- 
mals the brain is particularly sensitive to blood-pressure and the intra- 
cranial sinuses are considered a special arrangement for preserving uni- 
formity of pressure at all times. On this point, Foster, 94, p. 828, says: 
“The channels for the venous blood of the brain are not veins but 
sinuses, not so much tubes for maintaining a uniform current as longi- 
tudinal reservoirs, which, while affording an easy onward path, can also 
be easily filled and easily emptied, and in which the blood can move to 
and fro without restriction of valves. This arrangement is correlated to 
the peculiar surroundings of the brain, which is not like other organs 
protected merely by skin or other extensible or elastic tissue, but is en- 
cased in a fairly complete inextensible envelope, the skull. As a conse- 
quence of this, when at any time an extra quantity of blood is sent from 
