64 THIRD REPORT — IS33. 



human foetus, and the existence of one and the same funda- 

 mental type in the hrain of man and of the inferior animals. 



The facts which have been unfolded by the industry of Tiede- 

 mann, besides leading to the universal law of nervous develop- 

 ment, throw important light upon nervous function : for it is 

 observed that the successive increments of nervous matter, and 

 especially of brain, mark successive advances in the scale of 

 being ; and, in general, that the development of the higher in- 

 stincts and faculties keeps pace with that of brain. Thus, in 

 the zoophyta, and in all living beings destitute of nerves, no- 

 thing that resembles an instinct or voluntary act is discovera- 

 ble. In fishes the hemispheres of the brain are small, and 

 marked with few furrows or eminences. In birds they are 

 much more voluminous, more raised and vaulted than in rep- 

 tiles ; yet no convolutions or anfractuosities can be perceived 

 on any point of their surface, nor are they divided into lobes. 

 The brain of the mammalia approaches by successive steps to 

 that of man. That of the rodentia is at the lowest point of 

 organization. Thus the hemispheres in the mouse, rat, and 

 squirrel are smooth and without convolutions. In the carnivo- 

 rous and ruminating tribes, the hemispheres are much larger 

 and marked by numerous convolutions. In the ape tribe the 

 brain is still more capacious and more convex ; it covers the 

 cerebellum, and is divided into anterior, middles, and posterior 

 lobes. It is in. man that the brain attains its greatest magni- 

 tude and most elaborate organization. Sommerring has proved 

 that the volume of the brain, referred to that of the spinal mar- 

 row as a standard of comparison, is greater in man than in any 

 other animal. 



Various attempts have been made of late years, chiefly 

 by the French physiologists, to ascertain the functions of the 

 brain by actual experiment. It will appear from a detailed 

 survey of their labours, that little more than a few general 

 facts respecting the function of its larger masses and great na- 

 tural divisions have flowed from this mode of research. The 

 offices of the smaller parts of cerebral substance cannot with 

 any certainty be derived from the phenomena that have been 

 hitherto observed to follow the removal of those parts, since 

 the most practised vivisectors have obtained conflicting results. 

 Nor is it difficult, after having performed or witnessed such 

 experiments, to point out many unavoidable sources of fallacy. 

 In operations on living animals, and especially on so delicate 

 an organ as the brain, it is scarcely possible for the most skilful 

 manipulator to preserve exact anatomical boundaries, to restrain 

 haemorrhage, or prevent the extension to contiguous parts, of 



