MORPHOLOGY 57 



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

 neutral reaction, but never an acid one. The protoplasm of the higher plants 

 coagulates at a temperature not much over 50 3 C., in the Sehizophyta, however, 

 usually 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 a temperature as high as 105 U C. 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) ; sulphuric acid, if sugar be present, rose red. Acid nitrate of mercury 

 (MiLLON's reagent) gives to protoplasm a brick-red colour. 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 specimens, when the cell contents are not to be investigated. All of the 

 above-mentioned reagents kill protoplasm ; until they have done so, their char- 

 acteristic 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 also 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, hcematoxylin, safranin, iodine green, acid fuchsin, eosin, methylene 

 blue, and aniline bhie, 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 OHIIOMATIN. In 

 addition to those substances, which are to be regarded as integral parts of active 

 protoplasm, it always includes derivative products of albuininatcs, particularly 

 amides, such as asparagin, 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, which possess 



