834 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Some organisms, morphologically alike so far as appears with our 

 present means of investigation, behave very differently with the same 

 staining agents. The chemical affinities are not always the same 

 dui'ing life and after death, and there seems to be some relation 

 between the diversity of constitution of the protoplasm, revealed 

 to us by the diversity of the reactions, and the physiological or patho- 

 genic role of certain microbia. In other terms, where there are no 

 morphological species, reagents like inoculations show us distinct 

 physiological species. 



Is it not remarkable, for instance, that dahlia violet, methyl 

 blue, and iodine green, which, managed carefully, only colour the 

 nucleus of living infusoria, also colour, but always entirely, a great 

 number of rods and bacterian filaments ? We are thus led to con- 

 sider the chromatic elements of the protoplasm as diffused in the 

 microbia, whilst they are differentiated and condensed under the form 

 of nucleus or nucleolus in the infusoria properly so called. 



If, on the other hand, we consider that in the cells and infusoria 

 the transformations of the nucleus and nucleolus always precede the 

 phenomena of reproduction, however much they differ, and that 

 generally these transformations largely modify the form of the 

 nucleus and nucleolus, we are less surprised to see the same bac- 

 terian rod in process of development pass, as Cienkowski has shown, 

 through phases corresponding with the very distinct forms from which 

 morphological species have been made." 



Dr. J. D. Macdonald has also issued a second edition of his 

 ' Guide to the Microscopical Examination of Drinking Water,' in 

 which he gives the following directions for collecting and examining 

 sediments: — 



When water is very turbid, from an obviously impure source, it is 

 easy enough to obtain a sufficient amount of sedimentary matter for 

 microscopical examination, and a just estimate of the unfitness of such 

 water for drinking purposes may be thus readily formed. But it more 

 frequently happens that the deposit, even after long standing, is but 

 slight, and when this is the case, we must have recourse to special 

 means, by which the whole or a large amount of the matters in sus- 

 pension may be concentrated or collected together within a small com- 

 pass. In the first place one of the tall glass vessels above described, 

 should be filled with the water to be examined, and a circular disk of 

 glass, resting on a horizontal loop at the end of a long aluminium wire 

 lowered to the bottom, when the whole arrangement, lightly covered, 

 must be set aside for 24 or 48 hours, as the case may be. 



At the end of the specified time, the water should be siphoned off 

 with a piece of indiarubber tubing, so as to leave only a thin stratum 

 of the liquid over the glass disk. This should now be carefully raised 

 and laid upon blotting-paper to dry its under surface and remove the 

 surplus moisture, when it may be at once transferred to the Micro- 

 scope, with a large piece of cover-glass so placed upon it as to exclude 

 all air-bubbles. An ordinary watch-glass may in some cases be sub- 

 stituted for the disk alluded to, with advantage, as being less likely to 

 permit the loss of sediment by overflow, which is certain to happen 



