140 REPORT—1874. 
thought, this function being more needed as powers of thought are developed which 
are less closely connected with sense; and accordingly the great transverse com- 
missure appears first, in any degree of development worthy of notice, in the Rodents 
along with the middle lobe. The increased size of the cortical layer and the number 
and depth of its convolutions probably give an increase in the amount of thought 
and in its analysis. And the cerebellum, connected as it is principally with the 
spinal cord, seems to be a store of force which, having been set in action by the 
contracted muscles through the posterior nerves, continues to maintain, through 
the anterior nerves, the stimulus to muscular action, so as to keep up the action of 
the muscles which have been set in action till it is altered or suspended by the action 
of other nervous centres. Thus no other development of the brain seems to have 
any tendency to give that extension to thought which was assigned to the three 
lobes. The conyolutions and the fibres improve the action of the brain rather than 
enlarge the range of its objects; but the development of each additional organ of 
intelligence extends the range of the objects of thought. And it is as superadded 
developments that the three lobes appear, both in the vertebrate series of animals 
and in the development of the embryo of man./ 
Lastly, it was shown that the course of development of cerebral function which 
had been inferred from facts was in accordance with the general analogies of deve- 
lopment, as giving the powers which were needed in the struggle for life; for 
the primary function of the cerebrum being to direct the actions of the body by 
the thoughts of the mind to the attainment of desirable ends, the intelligence of 
which it is necessary that it should be the instrument is knowledge of the ends 
and knowledge of the means. And the development of that intelligence consists 
of three steps—the power of thinking objects as desirable or undesirable, the power 
of thinking actions as leading to ends, and the power of knowing objects to be 
desirable and actions to be efficacious. Accordingly the first lobe of the cerebrum 
should be developed to combine in thought qualities with things as their substance, 
the second lobe shoal be developed to think acts in time with a view to their end, 
and the third lobe should be developed to think a fact with the belief which 
belongs to it as a case of a general principle. 
Along with the power of thinking each of these classes of objects would come, 
in a greater or less degree, in proportion to the other developments of the cerebrum 
—the power of thinking their relations and comparative attributes, and that of com- 
bining them with each other and with emotions, desires, and aversions. 
And if it were objected to these inferences that considerable portions of the 
cerebrum may be removed without any apparent mutilation of the powers of 
thought, it might be observed that the acts of the mind become by association so 
connected with each other, that in each thought there are many associated elements, 
and that the corresponding seat of cerebral activity should be not in one but in many 
localities throughout the brain. Even if some of these were removed, the action 
of the others would still by association elicit and be elicited by the accustomed 
impressions of the sensorium and stimulation of the centres of muscular action. 
On a new Form of Microscope for Physiological Purposes. 
By Ricwarp Caton, M.D. 
This paper consisted of a description of a microscope modified with a view to 
the easier examination of the tissues of warm-blooded animals. Hitherto the phe- 
nomena of circulation &c. could only be studied in the mesentery and omentum; 
this instrument is intended to render practicable the examination of other tissues, 
as, for example, the subcutaneous cellular tissue and the brain-membranes. The 
front half of the stage, as ordinarily constructed, is removed, so as to allow the 
body of the animal to be brought into close contact with the object-glass. A small 
glass trough, one third of an inch in diameter, containing salt-solution, is attached 
to the centre of the stage immediately under the objective. The piece of tissue 
to be examined is laid across the glass trough, and held in position by two pairs of 
small stage-forceps. As the object cannot be moved about on the stage so as to 
bring any part of it as required under the object-glass, a corresponding movement 
