192 THE JOURNAI, OF PHARMACOLOGY. 



Cut across, the hairs are more or less rounded. The hairs of most 

 of the fur animals are flattened more or less, so that on cross section they 

 appear elliptical. Sheep's wool on cross section is circular but never 

 regular, being more triangular or polygonal. 



Examination Methods and Microchemistry. 



It is but seldom possible to distinguish the structural characteristics of 

 wools and hairs, under the microscope, without previous preparation. It 

 can only be done in cases where the hairs are thin, white, or very light, 

 and not too full of air and having swelled up in water. Darker hairs 

 show their structure either indistinctly or not at all, the thin hairs more 

 distinctly than the dark. It is best to view the hair in water. While 

 doing this, it is well to take into consideration that their histological 

 characters can only be seen distinctly after they have completely swelled 

 up. As hairs are frequently oily from natural fatty exudations or materials 

 are so from their manufacture, it is essential that they are boiled with al- 

 cohol, washed with ether, or treated in some way that will remove the oil. 

 As the fatty exudations not only contain oils but also substances soluble 

 in water, it becomes frequently necessary, to insure the complete cleansing 

 of the hair, to wash it with distilled water, warmed if need be, after having 

 been treated with ether or alcohol. It is obvious that this soaked hair may 

 not be measured directly, otherwise the results would be too high. Ac- 

 cording to the measurements a human hair without medulla will swell up 

 10.67 percent.; a white alpaca hair, 13.7 percent.; an Angora hair, 10.2 

 per cent.; a cow's hair, 16 per cent. Hairs without a medulla will swell 

 up on the average of 10 to 11 per cent., those with a medulla 15 to 16 per 

 cent. Therefore it is necessary to deduct this from the hairs that have 

 been soaked in water in order to get a more correct measurement of their 

 diameter. But as in the most cases an absolutely correct measurement of 

 their diameter is not required, it has become customary to measure them 

 in water and accept this result as final, just as is the case in measuring 

 starch grains, for it is tacitly understood that their measurements are taken 

 while they are in a moist state. But if we desire to know the diameter of 

 a dry hair, it would be necessary to examine it in olive oil or in air. It is 

 to be noted that fatty oils make the wools and hairs very transparent and 

 the fatty exudations very soluble so that under the circumstances such 

 oils become good media for observation. 



In determining the diameter of wools and hairs it is to be taken into con- 

 sideration, that only the minority of hairs are exactly circular. In order 

 to determine the form of one it is necessary to make cross sections or cut 

 it in small pieces, and while examining it under the microscope twist it 

 about its axis by moving it with the coverglass. 



A special apparatus has been constructed to stretch the longer hairs and 



