THE JOURNAL OF PHARMACOLOGY. 193 



twist them while taut. With this apparatus one is enabled to determine 

 the diameter of a hair in a dry state. A simple but in most cases effectual 

 method is the following : On a slide, or in cases where the hair is long 

 on a thick and about 4 cm. broad piece of glass, fasten a cork on both ends 

 by means of sealing wax, and through each of these corks draw an iron 

 wire. These pieces of wire, by turning up their outer edges, have become 

 transformed into a sort of crank and can be turned about their axes. To 

 the inner ends of the wires, also by means of sealing wax, fasten the hair 

 to be examined. This can now be easily truned about its axis and stretched 

 as desired. 



Cross sections of thick hairs, bristles and quills, these are absolutely 

 necessary to determine their structure, can easily be made by stretching 

 them between two corks, as above, and cutting them with a sharp razor. 

 Thin, soft hairs are placed upon a slide and are soaked with a thick muci- 

 lage containing some glycerin, dried, and then cut through cork. Good 

 sections may also be obtained by pouring melted paraffin over them or 

 cutting them, according to Reissner,* in gutta percha. It is better to un- 

 twist curled hairs by stretching them on a small board for about twenty- 

 four hours, then heat a guttapercha tablet and press the stretched hair 

 into it. When the guttapercha has become hardened (this can be hastened 

 by placing it in cold water) it will after a little practice be easy to obtain 

 good sections. 



At times the individual tissues of the hair are to be isolated. This can 

 be accomplished with sulphuric acid or caustic potash. Applying sul- 

 phuric acid will cause the scales to separate singly or in groups, but coil 

 up very much so that their shape cannot be easily determined. In potas- 

 sium hydrate the hair swells up greatly and then by pressure can be easily 

 resolved into its elements, but these have become somewhat changed by 

 the swelling. It is according to Nathusius f most advantageous to use 

 concentrated ammonia. After treating the hair with ammonia for two or 

 three minutes all the epidermal scales will come off without having un- 

 dergone much change, and their form can be easily studied. The author 

 uses chromic acid which he finds to be very satisfactory, also cupric am- 

 monia for maceration. 



Nitric acid, which is used so extensively for macerating plant tissues, is 

 not at all good for the same purpose in the case of animal hairs ; but it is 

 to be mentioned that it colors all horny tissues an intense yellow and is 

 therefore useful as a reagent. 



Sugar and sulphuric acid impart a pink color to hairs. Dyes of all 

 kinds (fuchsin, anilin violet) are readily absorbed, also iodin. Boiling 



* Beitrage zur Kenntniss der Haare der Saugethiere und des Menschen. Breslau, 

 1854. 



t Das Wollhaar des Schafes, 1866, page 47. 



