504 British Association for the Advancement of Science. 



that, when they are filled with injection, the parts beneath cease to 

 be visible ; the vessels are as thick as the finger, and coiled, and 

 heaped up on one another to an almost incredible amount. The 

 contrast between the condition of the venous system in the great 

 northern diver and that in the gannet, as exhibited by Dr. Houston, 

 is important in establishing the uses of these reservoirs. 



The diver and gannet are both seafaring birds, but differ remark- 

 ably in their modes of seizing the fish on which they feed. The diver 

 swims under water after its prey, and remains at such periods long 

 out of sight ; the gannet pounces on it like an eagle, when discovered 

 by its quick-sighted eye near the surface of the water, and thence 

 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- 



