SECT. I MORPHOLOGY 57 



Active protoplasm generally gives an alkaline, and, under certain conditions, a 

 neutral i-eaction, but never an acid one. The protoplasm of tlie higher plants 

 coagulates at a temperature not much over 50° C, in the Schizophyta, however, 

 often not below 75° C. In the inactive dried condition, as in spores and seeds, 

 it can endure a still higher temperature without coagulating. The spores of 

 many Bacteria can withstand temperatures over 100° C. for a considerable time. 

 Treated with alcohol or ether, with acids of definite concentrations, with 

 bichromates of the alkali metals, or with corrosive sublimate, protoplasm quickly 

 coagulates, while at the same time insoluble proteid compounds are formed. 

 Coagulating reagents, accordingly, play an important part in microscopic 

 technique ; of especial value are those, which, while fixing and hardening the 

 protoplasm, change its structure in the least degree. As fixing and hardening 

 reagents for vegetable tissues, alcohol, 1 per cent chromic acid, 1 per cent acetic 

 acid, 0'5 to 1 per cent osmic acid, concentrated picric acid, or corresponding 

 mixtures of these acids, solutions of mercuric chloride and formaldehyde, are 

 used. Iodine stains protoplasm brownish yellow ; nitric acid, followed by caustic 

 potash, yellowish brown (xanthoprotein reaction). Acid nitrate of mercury 

 (Millon's reagent) gives to protoplasm a brick-red colour ; sulphuric acid, if 

 sugar be present, rose-red. These reactions occur with all proteid substances 

 though they are not absolutely distinctive of them. Protoplasm is soluble in 

 dilute caustic potash and also in eau de Javelle (potassium-hypochlorite), and 

 accordingly both of these reagents may be recommended for clearing sjiecimens 

 when the cell contents are not to be investigated. All of the above-mentioned 

 reagents kill protoplasm ; until they have done so, their characteristic reactions 

 are not manifested. A large number of albuminous bodies or albuminates have 

 been named which are said to enter into the composition of living protoplasm. 

 Most of these compounds are still ill-defined ; in nuclei the nucleins are most 

 important, but they are also found in the cytoplasm. They are characterised by 

 containing much phosphorus, and are not attacked by pepsin, and only with 

 difficulty by trypsin. Staining reagents have become an important help to 

 microscopic investigations for determining the composition of protoplasm. This 

 is due to the fact that the different constituents of protoplasm take up and retain 

 the stain with different degrees of intensity and energy. As a general rule, only 

 coagulated protoplasm can absorb colouring matter, although some few aniline 

 stains can, to a limited extent, permeate living protoplasts. For staining 

 vegetable protoplasts, which have been previously fixed, the various carmines, 

 hajmatoxylin, safranin, iodine green, acid fuchsin, eosin, methylene blue, and 

 aniline blue, gentian- violet and orange, have been found particularly convenient. 

 The different components of the protoplasm absorb the stains with different 

 intensities, and, when reagents are employed to remove the colouring matters, 

 they exhibit differences in their power to retain them. The nucleus generally 

 becomes more intensely coloured than the rest of the protoplasm, especially a part 

 of its substance, which is therefore called chuomatix. In addition to those sub- 

 stances, which are to be regarded as integral parts of active protoplasm, it always 

 includes derivative products of albuminates, particularly amides, such as as[)aragin, 

 glutamin ; also ferments, such as diastase, pepsin, invertin ; at times alkaloids, 

 and always carbohydrates and fats. The ash left after incineration also shows 

 that protoplasm always contains mineral matter, even if only in small quantities. 

 All such substances which do not enter directly into the composition of protoplasm, 

 but are only included within it, are designated by the term metaplasm. 



The Cytoplasm. — The cytoplasm of vegetable cells, whicli j^ossess 



