224 THE JOURNAL OF PHARMACOLOGY. 



separated into its woof and warp threads. The sample must be of such a 

 size that it contains all the kinds of yarn or thread fibers used in its manu- 

 facture. When the sample is coarse the piece will often be quite large. 

 Warp and woof threads are now placed side by side, one of each kind is 

 chosen and further examined. In simplest cases there will be but one 

 kind of woof and warp threads present therefore requiring the examina- 

 tion of but two fibers. 



In more complicated cases there may be ten and more different kinds of 

 yarns to be analyzed. In wdolen goods (also in other cases) threads are 

 not infrequently found which consist of two or three twisted yarn threads. 

 These must be untwisted and each thread must be examined separately. 

 Whoever desires to examine fabrics must be sufficiently proficient so as to 

 be able to recognize the fibers about to be examined with a moderately 

 low power (30 to 60 diametets). It does not sufiice to be able to recognize 

 them when magnified 200 to 300 times, for this high power is not applicable 

 when examining weaves in which there are hundreds or thousands of 

 fibers to be examined. It is necessary to view ten to twenty fibers at one 

 time and be able to recognize them, in order to make the examination with 

 sufiicient rapidit5^ It is indeed easier to recognize the fibers with a high 

 power but the general oversight is lost, and it easily happens that entire 

 bundles of fibers are overlooked. 



If when using the low power one fiber cannot be determined, the ob- 

 jective can easily be changed and the fiber examined and recognized with 

 the higher power, then continuing the examination with the low power. 



It will not be necessary to previously prepare the fabric or to separate 

 fibers chemically if thoroughly familiar with the fibers, but microscopical 

 tests are often desired and advisable notwithstanding. 



If, for instance, it is desired to determine rapidl}'- and positively whether 

 some cotton fibers are present in a sample of woolen goods, warm the 

 sample for a short while in dilute potash lye, wash it, and examine it 

 with a very low power. The sheep's wool hairs (in fact, all animal 

 fibers) will have become transparent, greatly swelled and distended, 

 whereas vegetable fibers will be sharply outlined, very refractive and 

 hardly swelled. 



Darkly dyed fabrics often consist chiefly of threads which, when ex- 

 amined microscopically, will appear opaque, very dark and structureless. 

 It is then necessary to remove the dye, which can easily be accomplished 

 by boiling the threads with acetic acid, sulphuric acid, dilute alkalis, 

 potassium carbonate, etc. 



When making a more thorough examination proceed in such a way 

 that each thread is examined separately, note the number of fibers of 

 which it consists, and the color and kind of fiber. 



In testing one sample four different kinds of w^rp threads and one wool 



