ZOOLOGY 



USE OF THE MICROSCOPE IN NATURAL HISTORY. 



THE microscope, as an adjunct to naturalists, has been of high service, 

 which, however, has been overrated. Dr. Walker Arnott, in the Proceedings 

 of the Royal Society of Edinburgh, observes : 



Microscopic differences are by themselves of little importance. To see is 

 one thing; to understand and combine what we see, another. The eye must 

 be subservient to the mind. Every supposed new species requires to be 

 separated from its allies, and then subjected to a series of careful observa- 

 tions and critical comparisons. To indicate many apparently new species, 

 is the work of an hour; to establish only one on a sure foundation, is some- 

 times the labor of months or years. In microscopical natural history, as 

 much scrutiny is required to prove a new form to be distinct from its allies, 

 as in chemistry to discover a new alkaloid, or in astronomy to demonstrate 

 the identity of two comets, A naturalist cannot be too cautious. It is 

 better to allow diatoms to remain in the depths of the sea, or in their native 

 pools, than, from imperfect materials, to elevate them to the rank of dis- 

 tinct species, and encumber our catalogue with a load of new names, so 

 ill-defined, if denned at all, that others are unable to recognize them. The 

 same object can be more easily attained by attaching them, in the mean- 

 time, to some already recorded species, with the specific character of which 

 they sufficiently accord. In all such cases, the question to be solved for the 

 advantage of naturalists is not whether the object noticed be a new species, 

 but whether it has been proved such, and clearly characterized. 







THE NERVOUS SYSTEM. 



Dr. Brown-Sequard, in a recent lecture in Edinburgh, exhibited some 

 Guinea-pigs which had been experimented upon some months ago, by cut- 

 ting certain nerves; the hinder limbs became paralyzed, but in time the 

 animals recovered the power of voluntary motion, attended, however, with 

 a very curious result the operator could put them into a fit of epilepsy 

 whenever he pleased. It appears that by the cutting of the nerves, the 

 animals lose sensation except in one cheek; and if that spot be irritated, a 

 fit is the immediate consequence. Another noticeable particular is, that the 

 lice which infest the animals, congregate on that spot, and nowhere else. 

 Whether it be that there is more warmth or more perspiration than on 

 other parts of the body, is not known; at any rate, physiologists are agreed 



