206 PHOTO-MICROGRAPHY [CH. VIII 



among these, fresh brains, and hardened brains have been photographed without 

 the slightest injury to them. Furthermore, as many specimens are so delicate 

 that they will not support their own weight, they may be photographed under 

 alcohol or water with a vertical camera and the result will be satisfactory as a 

 photograph and harmless to the specimen. 



A great field is also open for obtaining life-like portraits of water animals. 

 Freshly killed or etherized animals are put into a vessel of water with a contrast- 

 ing back ground and arranged as desired, then photographed. The fins have 

 something of their natural appearance and the gills of branchiate salamanders 

 float out in the water in a natural way. In case the fish tends to float in the water 

 a little mercury injected into the abdomen or intestine will serve as ballast. 



The photographs obtainable in water are almost if not quite as sharp as those 

 made in air. Even the corrugations on the scales of such fishes as the sucker 

 (Catostomus teres) show with great clearness. Indeed so good are the results 

 that excellent half tone plates may be produced from the pictures thus made, also 

 excellent photogravures. In those cases, as in anatomical preparations, where the 

 photograph rarely answers the requirements of a scientific figure, still a photo- 

 graph serves as a most admirable basis for such a figure. The photograph is made 

 of the desired size and all the parts are in correct proportion and in the correct 

 relative position. From this photographic picture may be traced all the outlines 

 upon the drawing paper, and the artist can devote his whole time and energy to 

 giving the proper expression without the tedious labor of making measurements. 



"While the use of photography for outlines as bases for figures diminishes the 

 labor of artists about one-half it increases that of the preparator ; and herein lies 

 one of its chief merits. The photographs being exact images of the preparations, 

 the tendency will be to make them with greater care and delicacy, and the result 

 will be less imagination and more reality in published scientific figures ; and the 

 objects prepared with such care will be preserved for future reference." 



"In the use of photography for figures several considerations arise : (i) The 

 avoidance of distortion ; (2) The adjustment of the camera to obtain an image of 

 the desired size ; (3) Focusing ; (4) Lighting and centering the object. 



(i). While the camera delineates rapidly, the image is liable to. distortion. 

 I believe opticians are agreed, that, in order to obtain correct photographic images, 

 the objective must be properly made, and the plane of the object must be parallel 

 to the plane of the ground glass. Furthermore, as most of the objects in natural 

 history have not plane surfaces, but are situated in several planes at different 

 levels, the whole object may be made distinct by using in the objective a dia- 

 phragm with a small opening. 



$338. Scale of Sizes and Focusing. (2). By placing the camera on a long 

 table, and a scale of some kind against the wall, the exact position of the ground 

 glass for various sizes may be determined once for all, and these positions 

 noted in some way. 



FIG. 169. Vertical Camera for photographing objects in a horizontal position. 

 The camera is attached to a double frame connected by bent metal pieces 

 fastened to the lower and sliding in a groove in the upper frame. The two frames 

 can then slide over each other without separating. For moving the outer frame a 

 rack work is put on the lower or inner frame and a pinion with a toothed wheel on 

 the outer one. This is turned by the wheel shown . To prevent the camera run- 



