THE SKIN AM> ITS Ai'i'ENU.U-J . 373 



diameter. These granules are also to be found in the protoplasm of 

 the cell ; they contain a substance capable of swelling freely, and 

 present many points of resemblance to the granules found in the 

 cells of the oviducts. 



These glands represent the poison-glands or lateral glands of toads, and the ear- 

 glands or parotids of Caecilia (Leydig) . According to Leroux *, Gratiolet and Cloe'z 3 . 

 the reaction of these glands in toads varies; according to du Bois-Reymond 3 the 

 reaction is. in frogs, acid ; Engelmann * found the reaction of these glands, in frogs, 

 to be neutral, frequently, however, with a tendency to either acidity or alkalinity. 



These glands correspond with the ' large glands ' of Hensche, the ' contractile 

 glands ' of Stieda. the ' large, dark glands ' of Eberth, and the ' large contractile 

 glands ' of Leydig's earlier publications. 



(2) The mucous glands are, as a rule, smaller, more numerous, 

 and more evenly distributed than the serous glands. Usually they 

 lie in such close proximity as almost to touch one another ; according 

 to Engelmann an average number of sixty is foimd in one square 

 millimeter; 011 the abdomen 62-68; flexor surfaces of the posterior 

 extremities in some' places 76, but in others only 30-40 ; on the webs 

 only 2-6 to the square millimeter. On the nictitating membrane 

 they are arranged in two or three parallel rows, are large, and closely 

 applied to each other. They are wanting on the deeper surface of 

 the nictitating membrane. 



The glands are generally rounded in form and have a short neck 

 (Fig. 229). Glands in the recent condition, and not fully con- 

 tracted, have a diameter of cro6-o*2i mm., the majority measure 

 o*i2-o - i6 mm. in diameter. The upper pole of the gland is usually 

 placed directly under the boundary between epidermis and out is, 

 and, as a rule, about o - o6-o*i mm. beneath the superficial surface 

 of the skin. The duct usually passes directly to the surface, in a 

 straight line. 



The structure of the glands corresponds, in general, with that of 

 the serous glands. Externally is a coat of connective-tissue, which 

 is, however, more firmly attached to the muscular coat than in the 

 case of the serous glands, and may easily be mistaken for a struc- 

 tureless basement-membrane 3 (Eberth). The muscular coat is very 

 thin, and consists of 16-20 flat, spindle-shaped fibres; extending 

 from the upper to the lower pole as in the serous glands. At a 



1 Journal de Medicine, Vol. XI. p. 75. 



- Comptes rendus. 1851, Vol. XXXII, p. 582. 



J Untersuchungen uber thier. Electricitat, 1830, Vol. I, p. 17. 



1 Arch. f. d. ges. Physiol., 1852, Vol. V, p. 505. 



5 Openchowski /. c.} describes a basemeut-uiembriine. 



