THE EARLY DAYS OF COMPARATIVE ANATOMY. 173 



provided the knife had been thrust into the fissure 

 between the cerebrum and the cerebellum, the position of 

 which the operator had prudently explored by private 

 dissection, a miracle was duly proclaimed by an amazed 

 and unsuspecting public. 



In the Cassowary they describe and figure the long 

 aftershaft of the feathers, and note the peculiar nature 

 of the stomach and its valve, although the dilated 

 duodenum is misinterpreted as a second chamber of the 

 gizzard. They compare, not without reason, the air sacs 

 of the bird with the branching lung of the Chamaeleon, 

 but the chapter fixes our attention on account of the 

 discovery of the nictitating membrane of the eye. This 

 they had seen before, and it is mentioned casually here 

 and there, but it was in the Cassowary that they were 

 stimulated to disclose the complete facts. It is a remark- 

 able piece of research, illustrated by simple workman- 

 like figures, and more detailed and trustworthy than many 

 modern versions. They describe, in addition to the six 

 normal muscles of the eye, the two muscles which draw 

 the membrane over the cornea, and they show that the 

 object of the movement is to keep the surface of the eye 

 clean. The mechanics of the origin and doubling of the 

 pyramidalis are understood and explained, and they 

 realise that the quadratus does something more than with- 

 hold the tendon of the pyramidalis from the optic nerve. 

 These are facts we have all at some time laboriously 

 verified for ourselves, and we can therefore extend our 

 sympathetic admiration to the men by whose genius and 

 labour they were first laid bare ; but the true merit of such 

 a performance is rather the obligation it imposes on pos- 

 terity of precise and exhaustive observation. 



The chapter on the Indian Tortoise is an instructive 

 display of the strength and weakness of the Parisians ; 



