6o 



NATURE 



[November 15, 1894 



in the suddenly slaughtered animal, to get from such experi- 

 ments light on the processes peculiar to the condition of life, 

 undoubtedly furnish the germ of much valuable knowledge. 

 But it is of the very nature of these experiments that they must 

 always remain difficult and restricted, for the living object, the 

 tissue-cell, is accessible to microscopic investigation only with 

 the greatest difficulty. Comparatively small difficulties in this 

 respect are offered only by the free-living cells of the organism, 

 as, for example, by the leucocytes or blood-corpuscles. And as 

 a fact, by the researches of MetschnikofT, Massart, Buchner, 

 Gabritchevsky, and many others, we have recently acquired 

 some important and wide-reaching expsrimental knowledge 

 concerning the vital phenomena of these very objects. 



" But if we place ourselves at the point of view of comparative 

 physiology which Johannes Muller represented throughout his 

 whole life with such success and energy, an intinitely broad 

 perspective opens itself up for cellular investigations. A com- 

 parative view shows one fact of fundamental importance, 

 namely, that elementary life-phenomena are inherent in every 

 cell, whether it be a cell from the tissues of higher animals or 

 from the tis-sues of lower animals, whether it be a cell of a 

 plant, or, lastly, a free cell, an independent unicellular 

 organism. Every one of these cells shows the general 

 phenomena of life, as they lie at the basis of all life, in their 

 individual form. With this knowledge, all that it is necessary 

 for the inquirer to do is to select for every special object of ex- 

 periment the fittest objects from the wealth of forms presented, 

 and with a little knowledge of the animal and plant world, such 

 forms really obtrude themselves on the attention of the experi- 

 menter. Accordingly, it is no longer necessary to cleave so 

 timorously to the tissue-cells of the higher vertebrate animals, 

 which, while alive and in normal environment, we can only use 

 for microscopic experiments in the rarest and most exceptional 

 cases ; which further, the moment they are isolated from their 

 tissues, are no longer in normal conditions, and quickly die or 

 give reactions that may easily lead to wrong conclusions and to 

 enocs. Much more favourable are the tissue-cells of many in- 

 vertebrate, cold-blooded animals or plants which can be more 

 easily investigated in approximately normal conditions of life ; 

 yet even these, as a rule, will not outlast protracted experi- 

 ments. But here appear as the fittest imaginable objects, for 

 cellular-physiological purposes, free-living unicellular organisms 

 — namely, protists. They seem to be created by nature ex- 

 pressly for the physiologist, for they possess, besides great 

 powers of resistance, the incalculable advantage of existing in 

 a limitless variety of form, and of exhibiting, as the lowest 

 organisms that exist, all phenomena of life in their simplest 

 conditions, such as are not to be found among cells which are 

 united to form tissues, on account of their one-sided adaptation 

 to the common life of the cellular colony. 



"Concerning the application of experimental physiological 

 methods to the cell, wc need be in no perplexity as :o which 

 we shall choose. In tlic luxuriant multiplicity of form which 

 this world presents, there can always be found for every pur- 

 pose a great number of suitable objects to which the most 

 different special methods can be capitally applied. 



" Wc can, to begin with the simplest method, apply in the 

 easiest manner imaginable to the free-living cell the method of 

 simple microscopic observation of vital processes. In this 

 manner mere observation has furnished us knowledge of the 

 individual life-phenomena of cells in many details, and also of 

 their mutual connection. Among the most recent achieve- 

 ments of this simple method may be mentioned only the ex- 

 tremely valuable knowledge concerning the more delicate and 

 extremely minute circumstances of fecundation and propagation 

 which Flemming, Van Beneden, the- llertwigs, Strasburger, 

 Boveri, and many others have gained in recent years, partly 

 from living cells and partly from cells fixed in definite 

 conditions of life. 



" Moreover, we can also conduct under the microscope vivi- 

 lectional operations on unicellular organisms in exactly the 

 same scope and with greater methodical precision than can be 

 done on the higher animaU. .Several inquirers, as Gruber, 

 Balhiani, and Hofer, have alrer\dy trodden Ihii path with great 

 •access, and a considerable group of researches has shown dis- 

 tinctly enough the ftuitfulncss which this cellular vivisectional 

 method of operation promises for the treatment of general 

 physiological problems. With this vivisectional method also 

 Koux, the llertwigs, and others conducted their splendid in- 

 vestigations on the ' mechanics of anitiiil evolution,' by showing 



what functions in the development of animals fall to the lot of 

 the different parts of the egg-cell, or to the first filial [cells that 

 proceed from their division. • ■ • 



" We can also apply here, in its whole extent, that powerful 

 physiological method known as the method of irritation, and 

 investigate the effects of different kinds of irritation on the life- 

 phenomena of the cell or of dift'eient cell-forms. The vegetable 

 physiologists have already collected a great mass of material in 

 this field. But also in the department of animal physiology a 

 great number of recent works have endeavoured to prove that 

 the phenomenon of irritation which takes place on the applica- 

 tion of chemical mechanical, thermal, galvanic, and luminous 

 stimuli to unicellular organisms are of the greatest importance 

 for the phenomena of life generally. 



'■ Finally, we can approach the life-phenomena of the cell 

 chemically, although in this direction only the very first begin- 

 nings have been made, seeing that the microchemical methods 

 have been hitherto little developed. Nevertheless, the labours 

 of Miescher, Kossel, .Vltmann, Zacharias, Liiwit', and others 

 have already shown that the microchemical investis;ation of the 

 cell has a future of great promise." 



INK-CRYSTALS. 



THE pictorial representations of the forms taken by 

 ice-crystals are familiar to everyone ; and many 

 young observers have been grievously disappointed with 

 the difference between nature's handiwork and artistic 

 fancy, as exemplified by the ice-crystals really seen and 

 those which embellish scientific works. These " ice- 



NO. 1307, VOL. 51] 



Fig, I, — C'ystals form:d !)>■ the Ev.iporaiion of Ink. 



flowers," as Tyndall called them, cannot always be con- 

 veniently produced, so a substitute for them, in the form 

 of " ink-tlowers," should be interesting to students of 

 crystallography. Dr. K. Troucssart describes in La 

 Nature how " fleurs de I'encre " can be procured, and 

 the accompanying illustration reproduces some of the 

 forms observed by him. The method employed is very 

 simple. A drop of ink is allowed to dry on a slip of 

 gliss, and observed under a microscope with powers of 



