10 TRICIIOLOGIA MAMMALIUM: 



lustre, considerable; direction, straight; undulated; button, spindle-shaped, succeeded by 

 a neck; shaft, cortex paved, divided into compressed pentagons, not well defined. 



Exception. The cortex of the hair of the Sloth, does not appear to be either scaly or 

 paved. 



DESCRIPTION OF THE HAIR OF THE THREE-TOED SLOTH, (Bradypus tridactylis.) 

 Specimen in the Academy of Natural Sciences, of Philadelphia. Length, 2 inches and 

 j^ths of an inch; color, dirty whitish-br wn stone color, which, when viewed under the 

 microscope, is found to be a mechanical mixture of irregular portions of the cortex, some 

 of which are dirty white, and others brown color. Button, white, transparent, spindle- 

 shaped ; length, T j of an inch; diameter, ^ of an inch; sheath, white, opaque, 

 encompassing and adhering to the button ; shaft, neck, cylindrical, naked, white, opaque 

 and translucent; length, ^ths of an inch; diameter, ^- ff of an inch, gradually tapering 

 from the centre both ways. Body, length, 1 inch T 9 oths ; flat; greatest diameter, (which is 

 at the distance of 1 inch and -j^ths from the neck,) J ff th of an inch, gradually tapering 

 both ways to a diameter of T ^o tn f an ' ncn - Tn cortex, of the color above stated, of 

 irregular, inelastic, brittle pieces, separated by dark lines, which sometimes open into 

 cracks or fissures, extending to the central portion of the hair. When the cortex is 

 removed, the cylindrical, elastic, central portion is seen of a diameter of ^y^ths of an 

 inch; sometimes a portion of the cortex may be removed, leaving the remainder adhering 

 to the central portion, and presenting a rugged outline. At others, the central portion 

 obtrudes from beneath the cortex, exhibiting their fibrous texture. The cortex will not 

 divide into fibrils, but may be broken into irregular pieces of white and brown colors. 

 The central part is divisible into fibrils. Apex, length, -^th of an inch, naked, cylindrical, 

 transparent and pointed. 



Ductility, Elasticity and Tenacity. One inch of the above hair, July 4th, 1849, Bar. 

 30, Ther. 76, Dew-point, 66. 



With 170 grains it stretched J^ of an inch, elasticity entire. 

 ISO " 



" 190 " " -fa " " minus ^ 



< 900 u u 10 u a u 3 



""0" "9*0" 



" 220 " " U " " ' Wv 



" 24 " " -B " " " TO 



" 250 " broke. 



While the hair was under the stretching operation, the sides of the cracks and fissures 

 of the cortex separated; and they closed when the weight was removed, which shows that 

 the central substance is ductile and elastic. 



The Wool of the same animal. The wool, when drawn out of the skin, is connected in 

 tufts of 5, 7, or 9 filaments, held together by small portions of epidermis, below which 

 a button is seen, and sometimes a button and sheath. Length, from 1 inch to 1$; 



