116 



OBSERVATIONS UPON THE SPLEEN. 



CHAPTER VIII. 



OBSERVATIONS UPON THE SPLEEN. 



The spleen is absent from all invertebrate animals without exception. It is also 

 wanting in the Amphioxua, the connecting links between Fishes and the higher 

 forms of the Mollusca. 



In the Cyclostomi and Lepadogaster, it is said to be of such small size as to be 

 readily overlooked. 



It varies much in size, form, and position, in different fishes. In the Stingray 

 (Trygon sabina) it is large and oval (Figs. 12 and 13). In the Hammerhead Shark 

 (Zygoma malleus) it is narrow and much elongated, as in the following figure : — 



Fig. 22. 



Fio. 23. 



Fig. 22. Stomach, spleen, and pancreas of the Hammerhead Shark (Zi/gmnn malleus) reduced one-half diameter. A. 



Superior portion of stomach. B. Stomach. C, C. Spleen. D, D, D. Small intestine. 1', P, P. Pancreas. 

 Fig. 23. Stomach, spleen, and pancreas of Congo Snake (Amphiuma means) reduced one-half diameter. A. Stomach. 



S. Spleen. I). Small intestine P. Pancreas. 



