810 SUMMARY OF CURUENT RESEARCHES RELATING TO 



means of rcconlirg tbc observations of tbo investigator. Tbo idea of 

 reproducing, by pbotograpby, wbat is seen in tbo Microscope, is so 

 captivating, tbat it is a matter for little surprise tbat so many undertake 

 tbo work, Tbcso remarks do not ai)ply to tbc pbotograpliing of pre- 

 parations fur tbe purpose of producing excellent pictures, but bear upon 

 tlic merits of tbo two mttbods as auxiliaries to tbo work-tublc, Tbat 

 tbe pencil is being unwisely neglected, owing to a too implicit reliance 

 on i)botograpby, is an unfortunate present tendency, especially for the 

 young investigator, who loses tbo training to accurate observation wbich 

 tbo conscientious use of tbe pencil brings. But botb tbe pbotograi>hic 

 camera and tbe drawing-prism bave tbcir advantages, and tlie investigator 

 can afford to dispense witb neitber, as, by tbcir judicious employment 

 — sometimes by tbeir combination — more satisfactory and valuable results 

 are obtained tbau are possible by any exclusive adbcrence to citber. 



An experience in pbotomicrograjiby, wbich warrants a full appre- 

 ciation of its value and capability, has taught that the most serviceable 

 and satisfactory tield of iibutography lies at the extremes of tbo table of 

 amplification, with very low (20 to 70 diam,), and with very high powers 

 (500 to 1500 diam.). Wbat drawing can equal, in beauty of detail, a 

 really good photograph of a suitable specimen taken with a fine low- 

 power objective ? who can draw fibrillaj of striated muscle, a group 

 of bacteria, or a delicately marked diatom in competition witb photo- 

 graphs ? Excellent pictures are made under ordinary magnifications 

 (200 to 350 diam)., but in the majority of cases there is much less cause 

 for congratulation. Under these circumstances, the conscientiously and 

 skilfully used pencil will produce a more valuable and satisfactory record 

 for the investigator than the camera. The reason that good i)hotograpbs, 

 with very low or very high powers, are so satisfactory is, tbat under both 

 conditions suitable lenses reproduce all tbe planes of tissue necessary 

 for a serviceable representation of the object ; nine times in ten this will 

 not be tbe case with tbe pictures demanded of tbe 1/4 or 1/6. While it 

 is unreasonable to expect tbe lens to reproduce more than the plane 

 accurately in focus, it is nevertheless true that this physical limitation 

 (reduced to a minimum by the thinnest possible sections) frequently 

 renders ])botographs, under medium powers, unsatisfactory substitutes 

 for more diagrammatic drawings. At tbe present time the investigator 

 who depends upon photographs for bis illustrations, finds himself con- 

 fronted by the pertinent question as to the manner in which his pictures 

 shall serve as journal illustrations. Tbat i)hotography, in its applica- 

 tions to book-making, is yet in its infancy, no one doubts ; that really 

 beautiful results are already accomplished by the best methods is equally 

 certain ; if, therefore, the liberality of the publisher places one of the 

 unexceptional "processes" at bis command, tbe investigator may feel 

 confident. Let him, however, be cautious as to where he places his 

 hopes when economy is consulted, for there is nothing more annoying 

 to tbe worker himself, or more unfortunate for the cause of photomicro- 

 graphy, than the dissemination of those monstrosities whose harsh black 

 and white masses, devoid of half-tone and detail, are supposed to "re- 

 produce " a really fine negative. 



Frequently, however, the use of the photograph is out of the question, 

 and the investigator or the artist must make the necessary substitute ; 

 by all means let it be the microscopist himself, for he will then have 

 tbe guarantee that the featui-e of the drawing, especially valuable, is 



