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TRANSACTIONS OF THE SECTIONS. 115 
minister and interpreter of the thoughts, feelings, and emotions of the mind, the 
author maintained that, in all cases of loss of speech which are of cerebral origin, 
there is involved either structural change or functional derangement in the nervous 
apparatus of the intellectual consciousness. The author briefly narrated two illus- 
trative cases out of a number which had come under his observation, one of struc- 
tural change, and the other of functional derangement, both of striking significance. 
But the point which he wished especially to impress upon every physiological 
psychologist was this, viz. that the power of giving utterance to our thoughts and 
ideas in appropriate language depends upon the due relation being maintained in 
its integrity between the centres of intellectual action and the encephalic motor 
centres through which the volitional power is exercised in articulate speech—in 
other words, between the cerebral hemispheres and the corpora striata. For 
thoughts and ideas might be moulded for expression in the seat of intellectual 
action, but the agency of the will or volitional power to give them utterance re- 
quires the integrity of the motor centres, through which the volitional impulses 
operate on speech. The author said a special cerebral organ had been assigned to 
the faculty of speech, and that the illustrious Gall was the first to locate it in the 
anterior lobes of the brain. Since his time the subject had undergone much dis- 
cussion in France, and conflicting evidence had been adduced. He adyerted to the 
hypothesis of Dr. Dax, that the left hemisphere of the brain was zts eaclusive seat, 
but to which he could not subscribe. The brain is a double organ; the functions 
of both hemispheres are identical, in harmonious accordance with the douhbleness 
of the organs of sense, as double inlets to knowledge. Professor Broca, who 
claimed the honour of being the first to discover that the third convolution was the 
seat of the faculty of articulate speech, was constrained to admit that the function 
was not exclusively exercised on the left side of the brain, although disease there, 
with hemiplegia of the right side, was almost universally characterized by aphasia. 
The author, in proof that the right hemisphere exercised the same function in regard 
to articulate speech as the left, adduced a case in which there was extensive disease 
in the left hemisphere, on the very site of Broca’s organ, and yet during life the 
faculty of speech was not impaired. 
On the Homologies and Notation of the Teeth of Mammalia. 
By W. H. Frower, F.R.S., F.LS. 
After some introductory observations, the author stated that the subject which 
he proposed to bring before the Meeting was an endeavour to ascertain how much 
of the generally adopted system of classification and notation of the teeth of the 
Mammalia—a system mainly owing to the researches of Professor Owen, whose 
labours in this department of anatomy no follower in the same field could fail to 
recognize gratefully—stands the test of renewed investigations, how much seems 
doubtful and requires further examination before it can be received into the 
common stock of scientific knowledge, and how much (if any) is at actual variance 
with well-ascertained facts. 
One of the most important of the generalizations alluded to is the division of 
the class Mammalia, in regard to the times of formation and the succession of 
their teeth into two groups—the Monophyodonts, or those that generate a single 
set of teeth, and the Diphyodonts, or those that generate two sets of teeth. 
The Monophyodonts include the orders Monotremata, Edentata, and Cetacea; all 
the rest of the class being Diphyodonts. The teeth of the former group are more 
simple and uniform in character, not distinctly divisible into sets to which the 
terms incisor, canine, premolar, and molar have been applied, and follow no known 
numerical law. The group is, in fact, equivalent to that to which the term Ho- 
modont has been applied by some authors. On the other hand, in the mammalian 
orders with two sets of teeth, these organs are said to acquire fixed individual 
characters, to receive special denominations, and can be determined from species 
_ to species, the animals so characterized being Heterodonts. 
The author then showed that among the homodonts, the nine-banded Armadillo 
qvas certainly a diphyodont, having two complete sets of teeth, and among the 
heterodonts, many were partially, and probably some completely, monophyodont. 
Qe 
