THE STRUCTURE AND DEVELOPMENT OF THE 

 AXILLARY GLAND OF BATRACHUS. 



LOUISE B. WALLACE. 



A STRIKING resemblance has long been known to exist be- 

 tween some of the Cat-fishes and the Toad-fish in the posses- 

 sion of a naked skin, powerful protective spines, and a sac, 

 with a more or less wide opening, behind and in the axil of the 

 pectoral fin. It has been thought not improbable that this 

 peculiar sac bore a close relation to the spines and supplied 

 them with poison to inflict dangerous wounds, although no 

 cases of poisonous wounds produced by these fishes are on 



record. 



At the suggestion of Dr. Whitman, I undertook to work 

 out the morphology and development of the gland and, if pos- 

 sible, to ascertain its function. 



The spinous dorsal in the Toad-fish is formed by three stout 

 spines and the gill-covers are also armed with spines, all of 

 which are erect when the animal is irritated and can give a 

 slightly painful sting. At the same time the pectoral fins are 

 thrown outward and forward until the large foramen of the 

 axillary gland is opened to its full extent, but whether or not 

 the gland is especially active at such a time has not been deter- 

 mined. When dissected out from the loose, underlying con- 

 nective tissue, this gland is found to be a pouch-shaped sac 

 with a tough, fibrous wall lined by a layer of epidermal tissue 

 which is thrown into minute folds, giving a wrinkled appear- 

 ance to the surface. The cavity is divided into chambers 

 varying from two to five in number, each chamber representing 

 a separate invagination of the skin. (Fig. I.) 



In Fig. II, an enlarged view of one of the folds of Fig. I, 

 are shown the six different kinds of cells found in the epider- 

 mal lining of the sac. (a) The superficial layer is characterized 

 by small, deeply-staining nuclei closely crowded together and 

 is extremely delicate, often torn off in sections, leaving (b), the 



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