142 



SCIENCE 



[N. S. Vol. XLI. No. 1047 



socket.^ A two and one half volt tungsten bulb 

 L, run by dry cell batteries furnishes the light. 

 Immediately in front of the light a removable 

 metal diaphragm, D, is inserted through a slot 

 cut in the side of the tube. The aperture in 

 the diaphragm has, for the sake of convenience 

 and clearness in drawing the figure, been repre- 

 sented much larger than it is desirable to make 

 it. A circular aperture of from one haK a 

 millimeter to a millimeter in diameter is a 

 convenient size. If it is desirable to change 

 the size of the light spot, a set of diaphragms 

 of various sizes can easily be made. A second 

 diaphragm, G, made of black cardboard and 

 held in place by being cemented on to a cork 

 collar should be inserted at the lower end of 

 the tube carrying the light. This diaphragm 

 serves to cut out any reflection from the inside 

 of the tube. Its aperture should be about five 

 times the diameter of that in the diaphragm, 

 D. A low-power objective will be found most 

 serviceable for projecting the light, as it brings 

 it to focus at a distance from the microscope 

 sufficient to allow the experimenter a clear field 

 of vision in directing the spot. It has also the 

 advantage of a greater depth of focus than a 

 high power objective, making it much easier 

 to keep the light spot in sharp focus on a mov- 

 ing animal. The adjustable A* lenses are 

 of about the right magnifying power and offer 

 the additional advantage of allowing consider- 

 able variation in the size of the light spot 

 without a change of diaphragms. 



The spot of light produced by this apparatus 

 is, of course, an image of the portion of tung- 

 sten filament not cut out by the diaphragm, D, 

 reduced as many times as the objective magni- 

 fies, and projected at the focal point of the ob- 

 jective. By the use of a moderately high- 

 powered lens the spot can be made as small as 

 it is possible to follow with the naked eye, and 

 absolutely without halo if the diaphragms are 

 properly adjusted. It is at the same time very 

 brilliant, and will be found to elicit a marked 



3 Sockets of a size which fits readily into a micro- 

 scope and which receive the standard sized flash- 

 light bulbs can be obtained of any electrical sup- 

 ply house under the name of "telephone booth 

 sockets. ' ' 



response from forms which are at all sensitive 

 to stimulation by light. With it I have forced 

 blow-fly larvffi to crawl in flgure-of -eight loops 

 only five or six centimeters in diameter. 



In using the light to follow a moving 

 animal, the barrel of the microscope is re- 

 moved from the stand and held in the hand 

 like a pencil. One can in this way direct the 

 light with great ease and precision. I have 

 found it so handled, very satisfactory both as 

 a means of exploring for photosensitive areas 

 and as a means of subjecting a limited region 

 to continued stimulation while maintaining 

 the surrounding tissues unstimulated. 



Bradley M. Patten 



School of Medicine, 

 Western Reseeve Univeesity 



THE AMESICAN PHYSIOLOGICAL SOCIETT 



The 27th annual meeting was held in the physio- 

 logical laboratories of the Washington Univer- 

 sity Medical School, St. Louis, Mo., December 28- 

 31, 1914. Fifty-six of the societies' 208 members 

 were present. Five scientific sessions were held, 

 three of these being joint meetings with the other 

 societies of the federation, at which the following 

 papers and demonstrations were presented: 



W. B. Cannon, C. A. Binger and E. Fitz, "Ex- 

 perimental Hyperthyroidism. ' ' 



H. K. Basinger and A. L. Tatum, "Studies on 

 Experimental Cretinism. ' ' 



W. L. Gaines, "The Action of Pituitrin on the 

 Mammary Gland." 



George B. Eoth, "The Several Factors Involved 

 in the Standardization of Pituitary Extracts." 



H. C. Dallwig, A. C. Kolls and A. S. Loeven- 

 hart, "The Eelation between the Erythrocytes and 

 the Hemoglobin to the Oxygen of the Eespired 

 Air. ' ' 



J. A. E. Eyster and W. J. Meek, ' ' The Path of 

 Conduction for the Cardiac Impulse between the 

 Sino-auricular and the Aurioo-ventricular Nodes. ' ' 



C. Brooks and A. B. Luckhardt, "An Experi- 

 mental and Critical Study of Blood Pressure 

 Methods. ' ' 



F. C. Becht and M. McGuigan, "Mechanical 

 Factors in the Flow of Cerebro-spinal Fluid." 



Katherine E. Drinker and C. K. Drinker, "The 

 Effect of Eapid and Progressive Hemorrhage upon 

 the Factors of Coagulation." 



