GENERAL REMARKS ON THE SENSES. 549 
so may be regarded as modified epithelial cells, with which are 
associated a vascular and nervous supply. These end-organs 
are at once protective to the deli- 
cate nerves which terminate in 
them, and serve to convey to the 
latter peculiar impressions which 
are widely different in most in- 
stances from those resulting from 
the direct contact of the nerve with 
the foreign body. All are ac- 
quainted with the fact that, when 
Fia. 899.—Corpuscle of Vater (after Sappey). 
Fie. 400.—End-bulbs (corpuscles) of Krause (after Ludden). A, from conjunctiva of man; 
B, from conjunctiva of calf. It may be noticed that in all these cases the nerve loses its 
non-essential parts before entering the corpuscle. 
the epithelium is removed, as by a blister, we no longer possess 
tactile sensibility of the usual kind, and experience pain on 
contact with objects; in a word, the series of connections neces- 
sary to a sense-perception is broken at the commencement. 
Seeing that all the end-organs on the surface of the body 
have a common origin morphologically, it would be reasonable 
to expect that the senses would have much in common, espe- 
cially when these organs are all alike connected with central 
nervous cells by nerves. Asa matter of fact, such is the case, 
and in every instance we can distinguish between sensory im- 
pulses generated in the end-organ, conveyed by a nerve inward, 
and those in the cells of these central nervous systems, giving’ 
