400 Journal of Comparative Neurology. 



although it proved very fickle, is perhaps most suggestive, 

 especially in revealing the non-medullated fibers and endings, 

 but it would have been insufficient unless supplemented by the 

 other methods. Non medullated nerve fibers were brought out 

 by the Golgi only. The structure of the stroma was shown 

 best by the iron haematoxylin, while the haematoxylin and 

 picro-carmine gave the arrangement and relation of parts more 

 satisfactorily. 



Vibrissse being modified hairs, the interest centers around 

 the parts most differentiated. At a glance the follicle is seen 

 to be very large and deep and the gland very small. 



On closer inspection the absence of erector muscles is no- 

 ticed, while a somewhat complicated haemostatic apparatus 

 takes their place. The erectile apparatus lies within the corium 

 sheath and, in fact, all the structures peculiar to the vibrissa lie 

 between this sheath and the outer sheath of the hair proper. 



A short distance below the gland the hair sheath is en- 

 larged or thickened and above this swelling and between it and 

 the gland is an annular band of nerve fibers encircling the 

 sheath ; these are visible in the Golgi preparations and are seen 

 to connect with ascending fibers running parallel to the shaft 

 of the hair. 



Encircling the hair and its sheath slightly below the swell- 

 ing is a body of sponge-like appearance whose structure is, at 

 first, somewhat difficult to make out. This may be called the 

 pulvinus. It is a typical erectile tissue composed of loops of 

 capillaries so arranged as easily to expand when gorged with 

 blood and each capillary is provided with fenestrules through 

 which the blood is permitted to escape into the general lacunal 

 space in which these capillaries lie. 



Around the pulvinus is a large space filled to a greater or 

 less extent with a coagulum of lymph and corpuscles. The 

 whole apparatus is therefore an admirable provision for produc- 

 ing a sudden turgor and erection of the capsule and a rigidity 

 of the hair and it can hardly be doubted that the apparatus is 

 under close nervous control. 



Nerve fibers penetrate the corium sheath near the base of 



