690 



PHYSIOLOGY. 



as conclusive. Wedenskii, however, by experi- 

 ments on the action of a feeble polarizing cur- 

 rent upon the nerve, was unable to find any 

 evidence of the exhaustion of the nerve after 

 the tetanic stimulation had continued for six 

 hours. This unexpected resistance of the nerve 

 to what had been supposed to be the exhaust- 

 ing effects of continued activity on irritable 

 tissues suggested the question whether a nor- 

 mal nerve-fiber can be fatigued by any amount 

 of activity. Recent experiments by Prof. H. 

 P. Bowditch upon the nerves of a cat confirm, 

 by a different method of investigation, the 

 results reached by Wedenskii, and give sup- 

 port to the theory that nerve-force is trans- 

 mitted by some sort of molecular vibration, 

 after the manner of light and electricity. 



Prof. Manly Miles has recorded the results of 

 experiments made at the Massachusetts Agri- 

 cultural College upon the unconscious bias in 

 walking of forty-nine students of the three 

 higher classes in the institution. The subjects 

 experimented upon exhibited many variations 

 in respect to the relative length and strength 

 of their right and left legs, and the dominance 

 of their right and left eyes, as well as in right- 

 handedness and ambidexterity ; but these dif- 

 ferences did not appear to exercise any definite 

 material effect on the bias; and from these 

 facts the observer concludes that the cause of 

 the bias is not to be found in the mechanical 

 proportions, or relative strength, nor, proba- 

 bly, in the dexterity, of the legs. This bias, he 

 further remarks, "is obviously the result of 

 vital activities, involving complex actions and 

 reactions in the nervous system, which may be 

 defined in general terms, while the details of 

 the obscure changes taking place in the nerv- 

 ous system can not, in the present state of our 

 knowledge, be fully traced. Moreover, it is 

 evident that the phenomena in question must 

 be studied from the same stand-point as other 

 biological processes which can not be explained 

 or expressed by purely physical or chemical 

 conditions." 



In his address before the British Association 

 on the phosphorescence of marine animals, 

 Prof. H. 0. McTntosh spoke at some length of 

 the cause of the phenomenon. In the Protozoa 

 the structure of the minute and often very nu- 

 merous creatures which evince phosphores- 

 cence, shows that the presence of a definite 

 nervous system is not necessary for its mani- 

 festation. The protoplasm of their body is in 

 itself sufficient for its production. Here there 

 are no glands for the secretion of luminous 

 substances, and in many there is evidently no 

 fat which might undergo slow combustion. In 

 the Coelenterates the phenomenon seems to 

 stand in close relation to nervous processes, 

 though in certain cases the luminous substance 

 possesses peculiar properties. While in certain 

 annelids there exist glands which may effect the 

 secretion of a luminous substance, in some Poly- 

 noides the emission of light seems to be due to 

 a peculiarity of the nervous system. In the 



Crustaceans the luminous property appears to 

 possess the character of a secretion, which is 

 probably under the control of the nervous sys- 

 tem. In some animals death occasions the 

 manifestation of phosphorescence. It is hence 

 plain that the cause of the phenomenon is a 

 complex one. 



Herr Aronsohn observes, with reference to 

 the experiments of Herr Sachs and himself 

 respecting a heat -center in the cerebellum, 

 that when on a perfectly definite part of that 

 organ he pricked with a needle so deeply as to 

 touch the parts lying under the cortex, he ob- 

 served a rise of temperature in the rectum, the 

 skin, and the muscles, of from about 1 to 2 0. 

 The prick had to touch the corpus striatum, in 

 its mediate part, in order to produce the rise 

 of temperature. The increased heat continued 

 for about three hours after the prick, and ap- 

 peared on the two sides even when the wound- 

 ing of the brain was only one-sided. Electrical 

 stimulation of the same limited spot produced 

 a similar result. Experiments on respiration 

 and determination of the urea showed that 

 immediately after the corpus striatum was 

 pricked, the inhalation of oxygen and exhala- 

 tion of carbonic acid were increased, and the 

 secretion of urea was augmented. 



Special Senses. The question of physiological 

 pressure in the eye is of much importance, in 

 view of the fact that glaucoma is developed 

 through its pathological increase. By experi- 

 ments on the eye of the living cat, HerrGriin- 

 hagen found that everything increasing the 

 blood-pressure at the same time augmented the 

 intra-ocular pressure, while, on the other hand, 

 everything lowering the pressure in the prov- 

 ince of the carotid artery lessened the pressure 

 in the chamber of the eye. Stimulation of the 

 trigemini raised the intra-ocular pressure, as 

 did likewise stimulation of the medulla ob- 

 longata. The effect of atropine was a diminu- 

 tion of pressure. A few later observers have 

 yielded like results for the influence of the 

 blood-pressure, and deviating results for the 

 influence of the nerves and the alkaloids. Dr. 

 Holtzke, investigating the effects of three alka- 

 loids, ascertained that esoterine produced at 

 first a considerable augmentation of pressure, 

 and then an abatement of it to a point be- 

 low the normal; that pilocarpine produced 

 similar but less pronounced results; while 

 atropine called forth quite the contrary effects. 

 In the case of the pressure in the vitreous hu- 

 mor, which is still more directly connected 

 with glaucoma, Dr. Holtzke found it to b 

 always similar to the pressure in the anterioi 

 chamber of the eye. 



From some experiments made to ascertai 

 the time occupied by the act of accommoda- 

 tion of the eye in vision, Mr. J. W. Barrett cor 

 eludes that the accommodation apparatus acts 

 with varying degrees of rapidity, according t 

 different circumstances, the principal of which 

 are age, lesions of refraction, practice, indiv 

 ual characteristics, time of day, and fatigue. 



