1887.] natural sciences of philadelphia. 25 



January 25. 

 Rev. Henry C. McCook, D. D., Vice-President, in the chair. 

 Twenty-one persons present. 



The following were elected members; Bernard Persh, Geo. B. 

 Cresson, Joseph Whitehouse, William B. Marshall and William 

 Osier, M. D. 



Oti a Tumor in the Oyster. Prof. John A. Ryder remarked that 

 a few days since Professor Leidy handed him the soft parts of an 

 oyster, which he ;jaid he thought might be an interesting subject 

 for investigation, inasmuch as a very large tumor had grown into 

 the pericardiac cavity. The specimen is a very remarkable one, 

 and seems to be the first of the kind which has fallen under the 

 observation of naturalists; neither Professor Leidy nor the 

 speaker, in the course of large opportunities for observation, 

 having previously encountered anything of the sort. It is also 

 of great interest as proving that such pathological growths may 

 be developed in the mollusca, thus showing that even in the 

 invertebrata there may be morbid ^proliferations of certain tissues 

 which simulate in certain respects those observed to occur in 

 man and the higher types of vertebrates, in which they become 

 very dangerous and painful in character, as in the case of cancer. 



The first and most striking features of this tumor, found in 

 the oyster, is its great size in proportion to that of the animal. 

 The tumor in its largest dimension measures nearly one inch 

 across, with a thickness of fully half an inch. The total length 

 of the animal, in alcohol, is about three inches, and it appears 

 normal in every other respect. For size, in proportion to the 

 dimensions of the animal, it can therefore only be compared to 

 those huge morbid growths on certain parts of man known as 

 elephantiasis. It is subcircular in outline as viewed from the 

 side, and fills up the pericardiac cavity in front of the adductor 

 muscle; this cavity being very greatly enlarged in consequence 

 of the growth of the tumor. The larger portion of it also lies 

 on the right side, and on account of its great size it has displaced 

 the heart forwards and to the left. 



Its consistence is soft and yielding when pressed with the 

 finger, and consists of some eighteen very distinct lobules of 

 irregular size and form. Its joint of attachment appears to be 

 to the mass of tissue which surrounds the posterior and red: 

 part of the intestine of the animal, and ajDpears to have giwn 

 out in this region, or from the dorsal wall of the heart cbmnber. 



Upon removing one of the lobules, which was cut into /sections, 



it was found that its histological structure was also very remark- 



3 



