TRANSACTIONS OF THE SECTIONS. 
83 
carries it up to some dry spot, impaled on its long, sharp bill. As 
might be expected in those two birds of such opposite habits, the provi¬ 
sion of reservoirs for stagnant venous blood is largely developed in the 
one, but completely absent in the other. In the diver the venae cavae 
and venae cavae hepaticae are dilated to a size equal to that of the 
same veins in the adult human body, and there is, moreover, a kind 
of second auricle, designed to render the provision more complete ; 
whilst in the gannet these veins, and all the others in the body, are 
of the ordinary dimensions. 
Dr. Houston made allusion to the habits of pearl-divers, and offered 
a conjecture that in those individuals, to whom practice has given 
such a power of remaining long under water, some dilatation of the 
venae cavae and venae cavae hepaticae may be gradually effectuated, 
giving them their superiority over other men in suspending the breath, 
and approximating them thereby somewhat to the condition of aqua¬ 
tic mammalia. The dilatations which are known to take place in these 
vessels in some varieties of disease of the heart, he adduced in evi¬ 
dence of the possibility of such an occurrence. 
An Account of a Variety of Hydatid (Cysticercus tenuicollis) found 
in the Omentum of an Axis Deer ; with Observations on its Pa¬ 
thological Changes . By John Houston, M.D ., M.R.I.A., fyc. 
This hydatid, varying in size from an almond to an orange, gene¬ 
rally single, sometimes in connexion with another, lies in a smooth 
membranous cyst between the layers of the omentum. Its head and 
body are in the living state inverted into the cavity of the caudal 
vesicle; but by immersion in tepid water they become visible, 
and are always found protruded and naked in hydatids which 
have undergone death before the decease of the parent animal. 
Dr. Houston considers that the inversion of the head is the natural 
condition, and that its eversion is the result of some irritation 
or of death. He also differs from most other helminthologists, in 
being of opinion that the lateral depressions on the head, termed 
mouths, and visible only to the microscope, are covered over with 
a thin pellicle, and incompetent, therefore, to the office assigned to 
them, viz. that of being agents for the imbibition of nutriments, as 
he found that fluids squeezed from the vesicle in the direction of the 
head, protruded and rendered convex the membranes of these aper¬ 
tures before making its escape through them. Dr. Houston agrees 
in opinion with those who consider that the function of imbibition is 
carried on by the whole surface of the little animal. From the ex¬ 
amination of the specimens of hydatids which existed in great number 
and variety in this case, the author has been enabled to describe and 
delineate the different stages of the process of degeneration, to which 
he considers all such animals are by their nature subjected; and has 
arrived at conclusions as to the seat of these degenerations different 
from those advanced by other authors. He considers, That the term 
allotted for the existence of each individual hydatid having expired, 
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