1889.] ^'^ ' [Ryder. 



the skin of a living Ilyla carolinensia, if placed upon the human conjunc- 

 tiva, produces an intense burning sensation similar to and almost as un- 

 comfortable as that produced by red pepper brought into contact with the 

 same parts. This experiment with the secretion of Hyla the writer upon 

 one occasion accidentally inflicted upon himself. The acrid and poison- 

 ous properties of the secretion are therefore also probably protective in a 

 high degree to the various forms of liatrachia, which are otherwise but 

 poorly provided with organs of offense and defense. 



Another purpose which these glands also subserve is that of keeping 

 the skin constantly moist, in this manner making the integument more 

 efficient as a respiratory organ, such a function of the integument being 

 highly developed in the Salientia. 



It is not certain if these organs also serve as an excretory apparatus, but 

 it is highly improbable that an apparatus so highly differentiated as are 

 these epidermal glands of the Batrachia and which secrete so actively and 

 directly to the exterior, should not also be found to serve as emunctories 

 somewhat after the manner of the sudoriferous glands of Mammalia. I 

 therefore regard it as highly probable that they are also excretory in the 

 sense that they share in the process of the discharge of waste matters. 



As to their structure the following maybe remarked. They are ob- 

 viously formed in absolute continuity with the epidermis. They lie just 

 beneath the epidermis, or they may be said to be sessile or without any 

 stalk-like duct leading from the saccular portion to the epidermis to the 

 exterior. The canal, however, which passes from the gland through the 

 epidermis has flattened cells difierentiated in its walls, so that one may say 

 the efferent duct presents the character of a canal with a wall formed of 

 flattened elongated cells, the whole duct being embedded in the epidermis. 

 At the point where the saccular portion of the gland and its duct join 

 there is evidently a very gradual transition from the cells of the glandu- 

 lar part of the organ to those of its duct. Whether the smooth muscular 

 fibres which run nearly parallel with each other from the point where the 

 gland passes into the duct to the fundus of the latter are derived from the 

 epidermis or not cannot be made out with certainty from the structure of 

 the adult skin. These flattened muscular elements taper towards the duct 

 and converge toward one point at their opposite ends over the inner glob- 

 ular end or fundus of the gland. In teased preparations the relations of 

 these muscular fibres to the gland may be very distinctly seen, reminding 

 one somewhat of the manner in which the curved cycle of staves forming 

 the sides of a barrel are joined together by their edges. There is only one 

 layer of these smooth muscular fibres, though in some cases the edges of 

 two adjacent fibres seem to slightly overlap each other. The very inti- 

 mate union of the gland, its duct and its muscular investment, and the 

 close union of the whole to the overlying epiden«is, indicate very clearly 

 that the mode of origin of the structure is that which has already been 

 described, viz., a simple involution of the epidermis. The only part of 

 this whole structure the epidermal origin of which is in doubt are the 



PROC. AMER. PHILOS. SOC. XXVI. 130. 3P. PRINTED DEC. 12, 1889. 



