PHYSIOLOGY. 



545 



of time of safe anesthesia. The histological 

 changes, too, support this view. The changes de- 

 scribed in the cells were only transitory, and disap- 

 peared with the disappearance of the drugs from 

 the circulation and tissues, or soon after. Fur- 

 ther evidence was afforded that the moniliform 

 swelling of the dendrons was not due to simple 

 retraction of the neurons, but was the result of 

 a pathological change in the trophic center of the 

 neuron. It appears analogous to the swelling ob- 

 served in the first stage of atrophy in axons 

 when cut on" from their trophic centers. Kare fac- 

 tion of all substance and function of the monili- 

 form swellings may modify nervous functions, 

 and to such changes may perhaps be attributed 

 those losses of memory, slight manias, and melan- 

 cholias that are now and then reported to follow 

 prolonged anesthesia in the human subject. 



Special Senses. Describing studies of dilata- 

 tion of the pupil from stimulation of the cortex 

 cerebri, Herbert Parsons observes that the effect 

 is best obtained with slight anesthesia. It often 

 occurs without any movement of the eyes or body, 

 but most markedly in those epileptic convulsions 

 that often follow frequent or prolonged excita- 

 tion. It is never seen with deep anesthesia. In 

 the absence of epileptic conditions it is only ob- 

 tained from those parts of the brain which are 

 concerned in eye movements. When well marked, 

 dilatation of the pupil is accompanied by all the 

 usual effects of stimulating the cervical sympa- 

 thetic. The effect is sometimes more marked on 

 the opposite eye, and is diminished, but by no 

 means abolished, by section of both sympathetic 

 nerves in the neck. Other sympathetic effects are 

 abolished. It is not influenced by section of the 

 fifth nerves intracranially after previous section 

 of the cervical sympathetics, but is abolished after 

 such section of the third nerves. It is not abol- 

 ished on either side by section of the corpus callo- 

 sum. In the absence of the usual dilator tracts, 

 the effect is probably due to an inhibition of the 

 tonic action of the third nerves. 



The principal cause of irregular astigmatism is 

 found by F. J. Allen to be fibrous structure of 

 the crystalline lens. The three groups of fibers in 

 the lens cause unequal bending of the sight in 

 three different directions, so that a luminous 

 point appears to a normal eye to be surrounded by 

 three groups of radiating lines, in the form of an 

 inverted V. The author has tried to discover the 

 exact modus operandi of the lens fibers and its 

 bearing on ordinary defects of refraction and their 

 correction by glasses. It is not clear whether the 

 distortion is due to diffraction or to uneven re- 

 fraction. The following features can be demon- 

 strated by experiment: 1. The radiating lines 

 which appear on any side of the subjective ra- 

 tional image are caused by fibers which lie on 

 the same actual side of the lens. 2. The focus 

 of the aberrant rays is nearer the lens than the 

 proper or general focus, therefore convex spec- 

 tacles increase the distortion of the image, and 

 concave spectacles diminish it. 3. Distortion in- 

 creases as the pupil dilates, bringing the per- 

 ipheral fibers of the lens into the field. It follows 

 that convex glasses, which improve definition 

 in a good light, may sometimes cause blurring 

 when the light is weak enough to allow the 

 pupil to dilate widely. Irregular astigmatism 

 increases with age. Owing to presbyopia it may 

 not be apparent to the naked eye. But when the 

 general refraction is corrected by convex lenses, 

 the exaggerated distortion becomes evident. 



In an investigation of the monaural localiza- 

 tion of sound, Prof. J. R. Angell and Dr. Warner 

 Fite made observations on a person entirely deaf 

 VOL. XLI. 35 A 



in one car, with parallel o)>-,prv;ii ion-, in r-ome 

 cases upon a person \\itli nornm! ln-;n in;/. The 

 results point to qualitative (liil'rn-nro in "sounds 

 corning from different directions ;\ s MM \ t .\~\~ ,,f 

 the localizations. Such qualil.:ili\v ilitlVn-rirfH 

 may be due to the damping or recnloivirrj <,\ cer- 

 tain partial tones by the organs ot tin , :i , ,, n( j 

 head, and it is noteworthy that g<>ii"i;i.lly -<>ni<: 

 tones are unrealizable in monaural hearing. Th': 

 presence of eye-reiiexes was often very mmked, 

 and the final localization was frequently made on. 

 the basis of the eye-strain and the supposed direc- 

 tion of the sound. This statement, however, leaves 

 untouched the physiological basis of the eye- 

 movements. Finally, there is no good evidence for 

 supposing that extraneous sensations play any 

 part in the localization. 



Experiments were described by Prof. Hensen, of 

 Kiel, at the International Physiological Congress, 

 which afford evidence of the existence of an ac- 

 commodation mechanism for the ear. 



Miscellaneous. In the Wilde Lecture at Man- 

 chester, England, the subject being the microbian 

 flora of the human body, Dr. Elie Metchnikoff, 

 after describing the various microbian growths on 

 various parts of the body in the conjunctiva of 

 the eye, the follicles of the skin, the teeth, and 

 the digestive organs considered their functions. 

 Speaking of the greater rapidity with which 

 wounds inside the mouth are healed as compared 

 with those on the outer skin, he suggested that, 

 moistened by the saliva, such wounds remained 

 in contact with the microbes and their soluble 

 products, which stimulated the reaction of the 

 human organism. The secretions of the microbes 

 attracted a great number of white blood-cor- 

 puscles, which cleaned the wound cleared it of 

 microbes and mortified tissues and so favored 

 the process of recovery. In the lower parts of the 

 digestive system this function of microbes was 

 less important, the mucous membrane there being 

 much more seldom torn. But it was probable that 

 the acids secreted by many bacteria in the small 

 intestine rendered a real service by preventing the 

 development of certain other microbes which 

 might impede digestion. This preventive function 

 was also manifested in the course of conflict be- 

 tween the human organism and microbes of a 

 very dangerous kind, and there was reason to be- 

 lieve that in some cases the germs of Asiatic 

 cholera were rendered innocuous by the action of 

 the microbes which they encountered in the in- 

 testines. It had also been contended by some 

 authorities that the microbes in the digestive sys- 

 tem played an important part in the digestion of 

 food, arid that without them blood could not be 

 assimilated; but the data available would lead 

 rather to the general conclusion that for the nor- 

 mal action of the human digestion the presence of 

 the intestinal microbes was by no means indis- 

 pensable. They should now try to ascertain 

 whether the microbes in the human system might 

 injure its health. When the defensive forces of 

 the body flagged, the microbes of the skin began 

 to multiply and pour their noxious products into 

 the tissues and the blood. Boils and anthrax were 

 thus often developed in persons suffering from di- 

 abetes or other general disease. But the great- 

 est harm was done by the microbes of the stomach 

 and intestines. It had been recognized that the 

 gravity of the danger incurred in cases of per- 

 foration of the intestine was due to the inflam- 

 matory action of the microbes that escaped into 

 the peritoneum. The microbes further produced 

 soluble substances which' could be absorbed 

 through the wall of the intestines and so make 

 their way into the circulation. Several of these 



