ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 699 



bias. The tissues tberasolves liave been used as lantern slides, but higli 

 lantern power and intensity of liglit are requisite, and lie knows of but 

 two lanterns cajiable of such demonstration, one being the Strieker 

 lantern 



" Having stained a specimen, and thus made distinct the differentia- 

 tion of tissues, the advantage is again lost in the photomicrograph, 

 because, of course, the colouring is not reproduced, the j)icture being 

 only one of lights and shades. This has been remedied to some extent 

 by having the lantern-slides painted by hand, and by re touching, thus 

 making more prominent the outlines. Some have attained high excel- 

 lence in this art, but it is open again to the objection of bias. An artist 

 might colour his slide to prove his theories. Dr. Sudduth has experi- 

 mented arduously, hoping to iind a method by which he could colour 

 slides by such a j)rocess as would dispose of this objection, and enable 

 him to project on the screen facsimiles of the stained specimens, making 

 the lantern picture appear as does the specimen itself under the Micro- 

 scope. His exhibit proved that he has succeeded marvellously well. He 

 has done this not by hand-work, but by a process of toning in the dark 

 room. He has been specially successful in reproducing the purple and 

 pink of heematoxylin and eosin, Bismarck brown and gentian-violet. 



" He showed on the screen not only coloured slides, but also some 

 untinted. Conspicuous among these were beautiful specimens of the 

 forming blood-corpuscles in the mesoblast of the pig embryo, white 

 and red corpuscles of human blood, oval corpuscles from the thrush, 

 similar but larger ones from salmon, oyster-shaped corpuscles from the 

 frog, and a most beautiful slide showing the enormous corpuscles from 

 the Amphioma (a species of lizard). As showing comparative analogies 

 and differences between blood of various species these slides were 

 specially gratifying. . . . 



" Then began the specimens in colour. A slide showing stellate 

 reticulum exemplified how well he reproduces the hsematoxylin and 

 eosin stains. Next followed the apex of a tooth, showing Tomcs's fibres 

 retouched. Several slides wei'e shown of the rete Malpighii coloured 

 by hand, and also by the Doctor's method, which latter seemed vastly 

 more satisfactory and truthful. One of these in Bismarck brown 

 demonstrated how a single stain may be used, the lights and shadows 

 being differently affected; for which reason he thinks this particular 

 stain will prove most valuable. A specimen showing the pigment layer 

 of the retina in gentian-violet was much admired. A segment from the 

 mesentery was very clear and distinct. Stained with silver the result 

 was dark lines against a yellow background. Nuclei show as brown 

 points. A few slides in gentian-violet were shown, but this we were 

 told is the most difficult of the colours to manage. A very beautiful 

 slide was from a macroscopic specimen, stained methyl-green, a section 

 of the finger showing the soft tissues and the bone, also the forming 

 nail of a three months' human foetus. This was shown because it is the 

 only colour with which he has succeeded in differentiating the nail, 

 which usually appears so light that it is very indistinct. In this picture 

 it was quite plainly seen. Some slides followed showing develoj)ing 

 bone, cartilage, &c., and then one of special interest, showing the meso- 

 blastic tissue forming periosteum and pericementum, which is the first 

 differentiation into a membi*ane ; these two tissues, which so many claim 

 to be different, are shown to be similar, being similarly developed. 



3 c 2 



