378 



PRACTICAL HISTOLOGY. 



[XXXIV. 



FIG. 347. Tactile Corpuscles, Bill of Duck, 

 A. With three, and B. With two tactile 

 cells. The axis-cylinder terminates in the 

 tactile disc (black). 



and its sheath becomes continuous with the fibrous cupsule. So 



far these structures have been 

 found only in the bill and tongue 

 of birds, e.g., duck. They lie in 

 the corium, close under the epi- 

 dermis (fig. 347). 



3. T.S. Tongue or Bill of 

 Duck (G-randry's Corpuscles) 

 (L and H). Harden in i per 

 cent, osmic acid small pieces of 

 the marginal part of the tongue 

 or the sieve-like structure on 

 the edges of the mandibles of a 



duck. Treat other small pieces by the boiled gold chloride method. 

 (a.) Observe the tactile cells and discs as in fig. 347. 

 C. End-bulbs are small, oval, or cylindrical bodies of various 

 shapes. A nerve-fibre enters one pole, and as it does so it loses its 

 myelin and terminates in a softer granular inner core. The bulb- 

 which may be cylindrical in shape 

 consists of a tough fibrous cap- 

 sule continuous with the sheath of 

 eg, the nerve ; and a softer inner core 

 in which the axis-cylinder ter- 

 minates. Such bodies are found 

 in the connective tissue of the 

 mucous membrane of the mouth 

 and conjunctiva. It is not difficult 

 to isolate them from the conjunc- 

 tiva of a calf (fig. 348). They lie 

 in the sub - epithelial connective 

 tissue. Certain special forms of 

 them occur in the genital organs, 

 e.g., clitoris, and in connection with 

 joints. A special form is known 

 as Pacinian corpuscles. 



4. Pacinian Corpuscles (Cat). 



These are elliptical transparent bodies (2-3 mm. long and i mm. 

 thick), readily found in the meso-colon and mesentery of a cat. 

 They consist of many concentric fibrous laminae, arranged like the 

 coats of an onion, surrounding a central core, which is continuous 

 with the axis-cylinder of a nerve. The lamella are lined on both 

 surfaces by endothelium, which can be stained with silver nitrate 

 (fig. 350). The capsules are closer together near the centre than 

 they are at the periphery. Examine one fresh in normal saline, 

 and "fix" another with osmic ocid and mount it in Farrant's 



FIG. 348. End-Bulb from Human Con- 

 junctiva, a. Nucleated capsule ; l>. 

 Core; c and d. Nerve terminating 

 ind. 



