( 698 ) 
Place and form of this structure seem to me to justify the con- 
clusion, that in these cells is to be seen the homologon of the 
infundibular organ of the higher vertebrates. 
But is there any ground to see in it a sensory organ, and must 
we not attribute to it a glandular function? 
The clear aspect of the cells, even in sections stained with 
protoplasmic dyes, could lead us to put it down as a gland, sccre- 
ting a clear mucous substance. But the structure of the cells, the 
absence of any coagulated secretion on the free surface of the cells, 
the long cilia and the neurofibrillar structure inside the cells, the 
absence of any line of separation between secretion products and 
protoplasm inside the cells, is not favourable to that conclusion and 
seems to point at a nervous sensory function. 
If we then consider it to be a sensory organ reacting on a certain 
stimulus, the question arises: what is the stimulus. Could it be the 
variation of pressure inside the brain ventricle, as it may perhaps 
be the case with the infundibular organ of the higher vertebrates ? 
As yet there is no answer to the question. 
By van WIJHE the groove of Hatschek is homologised with the 
hypophysis of the higher vertebrates. If this be true, there is no 
primary connection between the infundibular organ and the hypophysis, 
for the chorda extends between them. 
In the higher vertebrates too this connection does not exist in 
all cases. For in some Teleostean larvae I could see the chorda sepa- 
rating the inf. organ and the pituitary body, by extending dorsally 
of the hypophysis and ventrally of the infundibulum. 
Amsterdam, April 1902. 
Physiology. — “The principle of entropy in physiology”. By 
Dr. J. W. LANGELAAN. 1st part. (Communicated by Prof. 
T. PLACE). 
Presented in the meeting of March 29th 1902. 
Crausrus deduced the two principal Jaws of the mechanical theory 
of heat from the premise that heat consists in a motion of smallest 
particles, and that the quantity of heat is a measure of the kinetic 
energy of this motion }). 
The first of these two principal laws states the equivalence of work 
') Crausrus, Mechanische Warmetheorie, 1887 1ster Bd. p. 23. 
si Sie ll i cena ae 
