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INSTRUCTION TO SCIENCE TEACHERS. 691 
the eye were studied. The structure of the eye was again exam- 
ined by each student, in specimens of those of the bullock, supplied 
in quantity, aud the internal ear and auditory ossicles were dem- 
onstrated in rough preparations of the sheep and rabbit. 
But little time could be afforded to physiology ; and, indeed, it 
was hardly possible that each member of the class should perform 
many physiological experiments for himself. The movements of 
the heart in the frog after excision, and the localization of the 
nerve-centre, was made out by each student ‘for himself; also the 
phenomena of reflex action in the frog, after the destruction of the 
cranial portion of the cerebro-spinal nervous system. Again, each 
table was supplied with simple galvanic forceps, and the irritation 
of nerve and of muscle examined, also the action of chemical and 
mechanical stimuli on the nerve. The action of curare poison on 
the frog (Berndrd’s experiment) was examined by every student, 
and the condition of the poisoned and the unpoisoned leg com- 
pared. Every member of the class was made familiar with the 
simplest way of demonstrating the circulation in the frog’s foot, 
tongue, and mesentery, under the microscope, and repeatedly exam- - 
ined the phenomenon for himself. Rigor mortis and the artificial 
rigor produced by warm water were examined. The conversion of 
starch into sugar by the saliva, and the methods of proving the 
presence of starch and grape sugar, were made the subject of 
experiment by every individual of the class. The peristaltic move- 
ments of the intestine and the absorption of the chyle by the lac- 
teals were exhibited and closely examined. A model of the 
circulation, consisting of india-rubber tubes and pump, was used 
for demonstrating the nature of the pulse, the pressure (by means 
of manometers placed in connection) in the arteries and veins, 
and the effect of dilatation and contraction of the capillaries 
and of rate of pulsation on this pressure. Finally, the thorax was 
opened in a narcotised rabbit and the heart exposed, and each 
student satisfactorily witnessed the pulsations of that organ and 
the inhibitory effect of irritation of the vagus nerve; the b 
pressure was exhibited to each member of the class in a aiy 
narcotised dog by means of the hemodynamometer, a a tube being 
placed in the animal’s carotid artery ; and as à concluding demon- 
stration the important fact of the influence of nerves upon gland 
secretion was demonstrated by the beautiful experiment of Ber- 
nard, the chorda-tympana being irritated, whilst a canula was 
AMER. NATURALIST, VOL. V- 44 
