TECHNIC. 405 



striation and occasional pigmentation. The medullary substance, if pres- 

 ent, may also be seen with its vesicles containing air. Both the cortical 

 and cuticular cells may be isolated, the process consisting in treating the 

 hairs for several days with 33 c / c potassium hydrate solution at room tem- 

 perature, or in heating the whole for a few minutes. Concentrated or 

 weak sulphuric acid produces the same result. On warming a hair in sul- 

 phuric acid until it begins to curl and then examining it in water, we find 

 that the cortical and medullary layers as well as the cuticle are separated 

 into their elements. Treatment of the skin with Miiller's fluid, alco- 

 hol, or sublimate is recommended for the examination of hair and hair 

 follicles. The orientation of the specimen should be very precise, in 

 order to obtain exact longitudinal or cross-sections of the hair. There 

 is hardly a structure of the body which is more suitable for staining 

 with the numerous coal-tar colors than the hair and its follicle (Merkel). 



The corpuscles of Meissner may be best obtained from the end 

 of the finger. After boiling a piece of fresh skin from the finger-tip for 

 about a quarter of an hour, the epidermis may be easily removed ; the 

 papillae are now seen on the free surface of the cuds. A portion of the 

 latter is cut away with a razor and examined in a 3 % solution of acetic 

 acid. The corpuscles are readily distinguished. Their relations to the 

 nerves should be studied in specimens fixed with osmic acid or gold 

 chlorid. The terminations of the nerves in these end-organs are best seen 

 in preparations stained after the infra vitam methylene-blue method. 



The corpuscles of Herbst and Grandry are found in the waxy 

 skin covering the bill, and in the palate of the duck (especially numerous 

 in the tongue of the woodpecker). For the study of the nervous ele- 

 ments the following method is useful : Pieces of the waxy skin are 

 removed with a razor and placed for twenty minutes in 50% formic acid. 

 After washing the specimens for a short time in distilled water they are 

 transferred to a small quantity of i c /c gold chlorid solution (twenty min- 

 utes), then again rinsed in distilled water, and placed for from twenty- 

 four to thirty-six hours in the dark in a large quantity (^ liter) of 

 Pichard's solution (amyl alcohol i part, formic acid i part, water 100 

 parts). After again washing in water the specimens are transferred to 

 alcohols of gradually increasing strengths and finally imbedded in celloidin 

 or celloidin-paraffin. 



The Pacinian corpuscles occur in the mesentery of the cat and 

 may be examined in physiologic saline solution. 



The nerves of the epidermis are demonstrated by the gold- 

 chlorid method (see p. 48). But even here the chrome-silver method and 

 the intra vitam methylene-blue method yield extremely good results, and 

 may be used with great advantage in the study of the nerves in the cutis. 



The so-called tactile menisci are very numerous in the snout of 

 the pig and the mole. Bonnet recommends for these structures fixation in 

 -33% chromic acid solution, overstaining with hematoxylin, and differ- 

 entiation in an alcoholic solution of potassium ferricyanid. 



