SCIENCE. 



[Vol. XXII. No. 545 



SCIENCE: 



Published by N. D. C. HODGES, 874 Broadway, New York. 



Subscriptions to any part of the World, 83.50 A year. 



To any contributor, on request in advance, one nundred copies of the issue 

 containing his article will be sent without charge. More copies will he sup- 

 plied at about cost, also if ordered in advance. Reprints are not supplied, as 

 for obvious reasons we desire to circulate as many copies of Science as pos- 

 sible. Authors are, however, at perfect lib 9rty to have their articles reprinted 

 elsewhere. For illustrations, drawings in black and white suitable for photo- 

 engraving should be supplied by the contributor. Rejected manuscripts will be 

 returned to the authors only when the requisite amount of postage accom- 

 panies the manuscript. Whatever is intended for insertion must be authenti- 

 cated by the name and address of the writer; not necessarily f r publication, 

 but as a guaranty of good faith. We do not hold ourselves responsible tor 

 any view or opinions expressed in the communications of our correspondents. 



Attention is called to the "Wants" column. It is invaluable to those who 

 use It in soliciting information or seeking new positions. The name and 

 address of applicants should be given in full, so that answers will go direct to 

 them. The " Exchange " column is likewise open. 



THE CAPABILTTIES OF PHOTOGRAPHY NOT UNLIMITED 

 FOR ILLUSTR..\TING ALL CLASSES OF OBJECTS. 



BY O. G. M.\SON, OFFICIAL PHOTOGRAPHER AT BELLEVUE HOSPITAL, 

 NEW YOKK CITY. 



The pomparatirely recent departure from old methods in vari- 

 ous fields of ecientific resea'cli. has called into action agencies 

 for sob ing problems of initial progress and results not known or 

 utilized by earlier workers. Di-coveries within tlie last few years 

 have so advanced the lines of study, and an active scientific press 

 has scattered so broa^lcast the knowledge of progress made that, 

 although the field is boundlf ss, he who reads has little excuse for 

 reworking ground from which all reachable fruit has been gath- 

 ered. In eagerness for the new, a desiie to find some hidden, 

 shorter paths into the mysteries of nature, do we not often fail (o 

 recognize obstacles, or to sufiiciently consider the best means f jr 

 their removal? With pen and pencil our predecessors s'lught to 

 leave a record of their work. What they thought and what they 

 saw have been handed down to us through the best means at their 

 command. For the physician, the botanist, mineralogist, and 

 the geographer the artist sketched, elaborated, and finished illus- 

 trations having a more or less amount of truth, often obscured by 

 some personality, which rendered them valueless or even mislead- 

 ing. In no class of objects have such defects been more con- 

 spicuous than that requiring the use of the microscope. Therefore, 

 he who had used with dissatisfaction the hands of the draftsman 

 was eager to utilize the means offered by photography. He had 

 seen the results obtaireti in other fields, and, without knowing the 

 diflSculties in the way, believed it easy to obtain all desired bril- 

 liancy, detail, and amplification. It may be asked. Why have 

 not these expectations been more fully realized? When we pause 

 to consider that color is a mo?t important feature in phi'tographic 

 work, and that a majority of objects studied under the microscope 

 reflect or transmit the least actinic rays of light, red, orange, 

 green, and yellow, we may well understand why we do not secure 

 brilliancy. Again, when the microscopist studies his subject for 

 detail, he mentally eliminates all those parts which do not belong 

 to the special point under observation. A crystal, cell, or fibre 

 which over- or underlies his objector forms a full or partial back- 

 ground in the field of the objective is left out in the mental sum- 

 ming up of his study. The laws of chemistry and optics do not 

 permit such selection and elimination from the photographic 

 mage. A slight tremor conveyed to the microscope by a passing 

 vehicle in the street, a step about the room or house, may be an- 

 noying to the observer, but does not prevent securing results by 

 longer application. But when we consider the necessity of abso- 

 lute immobility of the instrument, often for a consideiTble length 

 of time, in order to impress upon even the most sen'^itive plate 

 the image of many-colored objects, we can well understand one 

 of the greatest causes of failure to secure detail; and this obstacle 

 of motii n becomes far greater as the amplification increases. It 



is plain that motion is multiplied equally with the diameter of the 

 object; or, in other words, if we magnify an object one thou.sand 

 diameters, a motion of that object to the extent.of one-tl ousandtb 

 of an inch becomes in the amplified image a motion of one inch, 

 which very readily shows why good results cannot be obtained 

 under such conditions. When observing with the microscope, it 

 is po-sible and quite feasible to focus the instrument above and 

 below the general plane of the object, in order to study any pro- 

 jecting points which may be within or without the general plane. 

 This feature is not possible with the photographic process, save 

 in so far as diaphragming the lens and modifying the light may 

 effect the result. Owrestimation of the possibilities of photogra- 

 phy and Jtndprestimation of the careful preparation of objects 

 have occasioned much unnecessary labor and great disappointment 

 by failure to produce results which should be sought through dif- 

 ferent channels. When the investigator contemplates the em- 

 ployment of photography for illustrating his work, let him consult 

 his photographer before preparing his objects. No one human 

 being has yet encompassed all that is known. When the anato- 

 mist takes to his photographer a thick section of muscular or 

 ossified tissue and asks to have the individual striae and cells iso- 

 lated and delineated with distinct outlines and minute detail, he 

 will fail to realize his expectation. When the mineralogist or 

 geologist prepares his sections of crystallization or deposits, he 

 must not calculate that all his vai-ious planes will be perfectly 

 shown in one photograph, even if the specimen he translucent. 

 Colcr, mass, and position are important factors in all photographic 

 work. With orthochromatic plates many objects heretofore im- 

 possible of proper illustration may be quite successfully treated; 

 but, with objects of this class, another factor, that of time of ex- 

 posure, offers a barrier of limitation. The mobility of life, animal 

 and vegetable, is a most important element which cannot be ig- 

 nored in exposures of hours, or even minutes, and seconds. A 

 vegetable fibre, when placed in concentrated light, may make one 

 or more entire revolutions during the time of exposure necessary 

 to properly impress its image upon an orthochromatic plate; and 

 especially is this the case when a high-power objective is used. 

 Thin sections devoid of the less actinic colors, red, orange, yellow, 

 and green in their darker tints, or admixtures, may be easily 

 treated. Circulating fluids or objects changing size or position 

 are susceptible of instantaneous exposures only. When such ob- 

 jectionable features as motion and non-actinic color are present, 

 the problem becomes far more complicated, and if the photogra- 

 pher fails in its clear and complete solution his patron sometimes 

 looks upon such failure as a proof of incompetency or a lack of 

 proper effort. Like her sister handmaids in the advance and illus- 

 tration of scientific thought, photography stands ready to do her 

 proper work. She has done much, and it is believed will do more 

 to enlarge the field of human knowledge and gather the harvest; 

 but we should not ask her to accomplish the impossible. 



LETTERS TO THE EDITOR. 



»** Correspondents are requested to be as brief as possible. The tortzer's name 

 is in all cases required as proof of good faith. 



On request in advance., one hundred copies of the number containing his 

 covimunication loill be furtiished free to any correspondent. 



The editor loill be glad to publish any queries consonant with the character 

 of the journal. 



Worms on the Brain of a Bird. 



In the issue of Science for June 2, is a short account of my 

 finding thread worms in the brain cavity of Boturus miigitans. 

 The title of the article should have read "on" instead of " in, " 

 as they were not in the tissue of the brain but, as I state there, in 

 the subarachnoid space. 



Since writing the short article above referred to I have received 

 a card from Professor J. W. P. Jenks of Providence, R. I., in 

 which he gives an account of his investigation of a similar if not 

 the same parasite on the brain of the Snake Bird {Plotus anhingus). 

 To quote a little from his communication, he says : 



"In 1874 I camped for 50 days near Lake Akechobee in south 

 Florida, and shot dozens of the Snake Birds, and in 19 out of 20 

 mature birds found a bunch of 10 to 20 parasitic worms just 

 beneath the arachnoid membrane, but in no instance extending 



