106 LECTOEE IV. 



In instituting comparisons^ they must be confined to very 

 nearly allied groups : man can only be compared witb man ; ape 

 with, ape j the extension of this comparison to other animals is 

 not admissible. On examining the order of apes, for instance, 

 the influence of size is seen with the greatest distinctness. 

 Thus the small leonine tamarin and the marmoset monkeys have 

 no convolutions, the scarcely larger squirrel and tailed monkeys 

 have but few, whilst the large anthropoid apes, the orang, 

 chimpanzee, and gorilla, have very convoluted brains. 



The old anatomists paid but little attention to the arrange- 

 ment of the convolutions, specially as it was soon found that 

 they were not symmetrical on both sides. The sinuosities were 

 thus considered as accidental, or, as one naturalist observed, 

 as a confused mass of intestines, so that draughtsmen repre- 

 sented them in anatomical plates entirely conventionally. 

 Modem researches have, however, shown that, amidst this appa- 

 rent confusion, there exists a certain regularity, a definite 

 plan, which had not been detected for the simple reason that 

 inquiries extended to man only, in whom this irregularity of 

 the convolutions reached the highest degree. Naturalists were 

 in the same position as amateurs in architecture, who are un- 

 able to make out the ground-plan on account of the overloaded 

 ornamentation of a structure. 



No sooner was attention directed to animals and the more 

 simple phenomena analysed, than it became apparent that for 

 every family or order there existed a special plan, as regards 

 the arrangement of the convolutions, entirely characteristic of 

 the orders and easily traceable in the highest as well as in 

 the lowest forms. In the unconvoluted brain of a small lion- 

 monkey {Simia rosalia, Geofiiy), there is exhibited the same 

 fundamental plan of arrangement as in the convoluted brain of 

 the orang, and the incomparably more convoluted brain of man. 



I may be allowed, perhaps, to dwell for a moment on this 

 result of recent investigation. There is no doubt whatever 

 that, according to the fundamental plan of his brain, man be- 

 longs to the ape. " On comparing," says Gratiolet, " a series 

 of human and simian brains, we are immediately struck with 

 the analogy exhibited in the cerebral forms in all these creatures. 



