E. Schuster 
4G7 
deaf relatives excluding brothers, sisters and children ; whether the deafness was 
congenital or if not at what age it occurred, and to what cause it was attributed ; 
the schools at which they were educated, and lastly there is a broad space left for 
remarks. The remarks consist mostly of indicating whether the husband or wife 
was related to, or had been married to, or was subsequently married to, any other 
of the husbands or wives, whose marriages are recorded in the tables. Where any 
of these particulars could not be obtained, a dotted line is ruled across the space 
in the table in which it .should have been set down. The first part of the book 
consists of an analysis of the tables, but for various reasons 1 have not made any 
use of this part. 
Deafness. Deafness may be divided into two categories, congenital and 
"acquired" or "adventitious." Congenital deafness appears for the most part 
to be due to faults in the structure of the membranous labyrinth of the inner ear ; 
but the eighth nerve may also be affected, and in some cases the deafness results 
from defects in the central nervous system, which may coexist with perfectly 
formed ears. It is usually associated with an anomalous condition of the functions 
of balance, and much experimental work has been done recently in Germany 
on this point (by Pollak, Alexander, Kreidl, Hammerschlag, etc.). It may possibly 
be compared to the structural peculiarities of the semicircular canals of Japanese 
waltzing mice. 
Acquired deafness is due generally to changes in the middle and inner ears 
produced by inflammation, which may be idiopathic or set up by various diseases, 
such as meningitis, scarlet fever, etc. 
Should a child be born with the faculty of hearing not developed beyond 
a certain pitch, he will be unable to learn the art of speech in the ordinary 
manner, that is to say by imitating the sounds formed by the speech of others ; 
and should he lose his hearing before, or but shortly after, learning to talk, the 
effect will be the same. He may, however, be taught to speak in a fairly intelli- 
gible manner by special methods, which consist in causing him to imitate not the 
sounds themselves, but the different muscular movements that produce them. 
But in order that this may be done with success, there needs to be patience and 
skill on the part of the teacher and fair mental ability on the part of the pupil. 
In making the correlation tables contained in this paper, it has been impossible 
to separate congenital from acquired deafness, because one is only given informa- 
tion on this point for one set of people, as will be explained later, and not for their 
brothers or sisters or children. Also it is almost certain that a large number of 
congenital deaf-mutes are included in the adventitious class, as this is apparently 
considered a matter of less shame than to be born deaf. If a child is found to be 
deaf at the age when it should begin to speak, it is very difficult to say definitely 
whether it has been born deaf, or whether the deafness was produced by some 
disease in its infancy, so that when there is any possible pretext for attributing it 
to the latter cause, this is done. As the possession or non-possession of deaf 
