BIOLOGY. 325 



longing to the family Diatomacece, commonly called "Infusoria,'' 

 and placed by all writers in separate species of the genus Gom- 

 ])honema, attached together by the same common stalk in such a 

 way as show them to be but states of one species. Also, when 

 examining in the same way, during the present month, some plants 

 taken from the waters of New York harbor, he had found a form of 

 Schizonema and a form of Hommocladia^ both hitherto considered 

 distinct genera of Diatomacece, which grow within membranous 

 tubeis, in one and the same tube, thus connecting the two genera 

 in a novel manner. He said he was not yet prepared to account 

 for these remarkable occurrences, as the life-history of these or- 

 ganisms was as yet but imperfectly understood. 



BIOLOGICAL SUMMARY. 



Mental and Manual Labor. — Prof. Houghton, of Trinity College, 

 Dublin, has published some curious chemical computations re- 

 specting the relative amounts of physical exhaustion produced by 

 mental and manual labor. According to these chemical estimates, 

 two hours of severe mental study abstract from the human system 

 as much vital strength as is taken from it by an entire day of mere 

 hand-work. This fact, which seems to rest upon strictly scientific 

 laws, shows that the men who do brain-work should be careful, 

 first, not to overtask themselves by continuous exertion ; and, sec- 

 ondl}^ that they should not omit to take physical exertion on a 

 portion of each day, sufficient to restore the equilibrium between 

 the nervous and the muscular system. — Medical and Surgical Re- 

 porter. 



Eustachian Tube in Swallowing. — Prof. Cleland has answered 

 the question, Is the Eustachian tube opened or shut in swallow- 

 ing? He pointed out that this tube was not, as generally sup- 

 posed, shut, in ordinary circumstances, and opened in swallowing, 

 but opened in ordinary circumstances and spasmodically shut in 

 the act of swallowing. The proof of this position was based 

 partly on anatomical consideration, and partly on observations 

 made on a patient in whom the Eustachian tube was visible on 

 one side through an ulcerated opening, and whom he had taught 

 to swallow with his mouth open. 



Physiology of Pain. — Prof. Rolleston has said it was a common 

 mistake to suppose that pain was an exaltation and excitement of 

 function, for it might also be occasioned by a lowering of func- 

 tional activity, brought about mainly by starvation or shock. 

 Starvation was produced by a cutting off of the supply to the tis- 

 sues from the blood-vessels which, by an excessive action of the 

 vaso-motor nerves, contracted so forcibly as to cause the current 

 to cease. The pain from shock was pi-oduced by a sudden impact 

 without the intervention of blood-vessels, though not without the 

 intervention of the tubes containing nerve matter. 



Seat of the Faculty of Articulate Language. — According to Prof. 

 Paul Broca, the seat of this faculty is the third frontal convolution 

 of the brain (chiefly the left side), which, he said, acted upon the 



28 



