316 

 MICROSCOPIC OBSERVATIONS. 



By Thomas Taylor, Microscopist. 



It bas been decided by high authority that Bacterium* consisbs prin- 

 cipally of vegetable cellulose,t because, when subjected to a boiling 

 solution of the alkalies, it remains undissolved. When rod-bacterium 

 {Bacterium termo) is treated with a tincture of iodine, its interior struct- 

 ure is changed from its natural transparent whiteness to an amber 

 color, which indicates the presence of protoplasm- in its outer elongated 

 cell. It is popularly supposed that any object composed of vegetable 

 fiber must necessarily be devoid of animal life 5 and that, although 

 many microscopic germs exhibit animal motions in water, they may, 

 notwithstanding, be purely vegetable ; but it has been demonstrated 

 that parts of certain animals, as the mantle of the Tunicata, consist of 

 cellulose. It may therefore be reasonable to expect, as a necessary con- 

 sequence, the presence of analogous substances in them, such as animal 

 starch, gly.cogen,| and chitine, § which are convertible into each other. 



* One of the earliest organisms appearing iu decaying and putrefying animal and 

 vegetable solutions. 



t Cellulose is the characteristic tissue of the vegetable kingdom. It forms the fun- 

 damental layer of all vegetable cell-walls. The young parts of plants consist chiefly of 

 cellulose; it exists in a tolerably pure state in the pith of the elder-tree, (Johnston.) 

 More recently, according to De Luca, it is found in the skin of the silk-worm and of 

 serpents. B^champ says that it is found in the vibrating corpuscles of the silk-worm. 

 Lowig and Kolliker have recognized cellulose in the cartilaginous capsule of the sim- 

 ple Ascidiw, in the leathery mantles of the Cynthice, and the outer tube of the 

 SaJpce. 



Chemical 'properties of cellulose. — When cellulose is treated with oil of vitriol, con- 

 centrated hydrochloric acid, or a concentrated aqueous solution of chloride of zinc, it 

 yields products which are converted into glucose when their aqueous solution is boiled 

 with water. Glucose is likewise produced in the decomposition of lignosulphate of 

 lead, and by the action of alkalies on pyroxyline. But it is doubtful also whether this 

 sugar should be regarded as destro-glucose. According to B^champ (JV. Ann. Chim. 

 PhyS; 43, 502,) it yields, when treated with alcohol, two sorts of crystals, one sort hav- 

 ing the hardness of cane-sugar, the other resembling destro-glucose. 



The skin of the silk-worm and that which remains in the cocoons, when the butter- 

 flies escape, are capable of yielding a substance isomeric with cellulose, which may be 

 converted into glucose. When the caterpillars are boiled for several hours with strong 

 hydrochloric acid, and this treatment is repeated three times with the residue, and the 

 residue is washed with strong potash-lye, then with water, and dried between 100° and 

 110°, a white, light substance, nearly free from nitrogen, is obtained, which gradually 

 diffuses in oil of vitriol, forming a colorless gummy liquid. This solution added by small 

 quantities to boiling water, and boiled for an hour or two, yields fermentable sugar 

 which reacts like glucose with common salt and potassio-cupric tartrate. (De Luca, 

 Compt. Rend., 53, 102.) 



I Glycogen, a term generally applied to animal starch, so called, discovered by Vir- 

 chow, who found it iu degenerated liver and spleen ; also in diseased kidneys, brain- 

 granulations, and concretions of the prostate gland. He says such tissues assume a 

 reddish-brown or more rarely a dirty-brown violet color, when treated with tincture 

 of iodine. When treated with oil of vitriol and iodine in succession, they acquire a 

 green color, changing to a dirty violet or sometimes blue. (Gmelin's Chemistry, 

 vol. XVIII, p. 334.) 



$ Chitine resembles cellulose. It is supposed by some to be nitrogenous ; it 

 forms the elytra and integuments of insects and the carax)ace8 of Crustacea. 

 It may be obtained by exhausting the wing-cases of cockchafers successively with 

 water, alcohol, ether, acetic acid, and boiling alkalies. The final residue retains com- 

 pletely the form of the wing-cases. Fr^my prepares chitine by treating the tegument- 

 ary skeleton of a crustaceous animal with cold dilute hydrochloric acid, to removn 

 calcareous salts ; washing with distilled water; boiling for several hours with solutioe 



