November 22, 1889.] 



SCIENCE. 



353 



almost one hundred and fifty years the only comprehensive treatises 

 on the subject ? But the most charitable inquirer fails to find 

 during that long period any other works of importance on vegetable 

 •anatomy. 



Near the close of the last century, at a period characterized by 

 activity in many departments of speculative inquiries, the subject 

 of vegetable structure again excited considerable attention, but 

 little substantial advance was made. In 1804 the Royal Society of 

 Sciences at Gottingen proposed for competition certain questions 

 relative to the structure and the mode of growth of tissues. The 

 chief contestants for this prize were Link, Rudolphi, and Trevira- 

 nus. The memoirs of the first two received the prize ; that of the 

 latter, honorable mention. The names of others should be re- 

 ferred to as having worked at or about this time in the same field ; 

 namely, Bernhardi, Mirbel, and Moldenhawer, the last making a 

 great advance in certain directions. But to all of these whom I 

 have mentioned, including the winners of the prize, the important 

 ■question seems to be, how are the structural elements distributed, 

 rather than how are they related to each other in manner of growth 

 and as respects their origin. With the cell contents they had com- 

 paratively little to do. They were busy with the constituents of 

 the framework. 



There appears to have been a strong suspicion, on the part of 

 some botanists during that period, that all this study of the skele- 

 ton of the plant failed to go to the bottom of the question. The 

 ■only wonder is, that with their scanty and untrustworthy chemical 

 appliances, and with their very imperfect lenses, they accomplished 

 so much. May I remind you that the element iodine, which is the 

 most important re-agent in the examination of the contents of 

 vegetable cells, was not employed until the year 1812 ; and, further, 

 that no good achromatic and aplanatic lenses, of even moderately 

 high power, were constructed until 1827 ? 



Noting the more important discoveries of the next period in 

 their order, we come first upon that of the nucleus of vegetable 

 ■cells by Robert Brown in 1833, and one mode of cell-division by 

 Mohl in 1835. In 1S38 the eccentric Schleiden published his 

 "" Contributions to Phylogenesis," in which he states substantially 

 that cells of plants can be formed only in a fluid containing, as 

 •chief ingredients, sugar and mucus (schleijii). By this latter term 

 he designated the nitrogenous matters taken collectively. At his 

 touch all disguises fell, and for ihe first time the vegetable cell 

 was distinctly recognized as a unit of structure always serving as 

 the common basis for the formation of the mnumerable shapes of 

 the structural elements. 



Next comes the master, Mohl. Armed with the best optical ap- 

 pliance procurable, familiar with the use of the chemical re-agents 

 then at command, and accustomed to accurate research, he reviews 

 his own earlier work and that of his contemporaries, making rapid 

 advance in the knowledge of the contents of the cell. In 1844, in 

 a paper on the circulation within vegetable cells, he speaks of the 

 living mass in each active cell, and distinctly recognizes it as that 

 which is the treasury of stored energy and the vehicle of energy 

 under release. He describes it as that which builds shapely 

 forms out of unformed matter and at first hands. This substance 

 he names " protoplasma." 



If we look at the handbooks of botany just before this date of 

 the early forties, we find references to " coagulable matters " 

 {Treviranus), and the chemical instability of the substance within 

 cells was suspected of having much to do with its activity ; but 

 almost all of the notes, as well as those upon the same subject found 

 here and there in philosophical writings of the latter part of the last 

 century, are based on pure speculation. The scientific recognition 

 ■of a physical basis of vital activity must be credited to Schleiden 

 and Mohl. 



The term " protoplasm '' was at once adopted by Schleiden, and 

 a good substitute for the indefinite and misleading word schleim, 

 which he had employed to designate essentially the same sub- 

 stance, and it became thoroughly established in scientific termi- 

 nology. In 1850, Professor Cohn (and Unger in 1855) showed that 

 the protoplasm of vegetable cells is identical with what had been 

 described in 1835 in animal structures as sarcode by Dujardin, and 

 this prepared the way for the exhausti\'e treatise by Max Schultze 

 in 1858. From that date on, work in the contiguous fields of 



botany and zoology has made no physical or chemical distinction 

 between the living matter in animals and plants. Investigators in 

 the two fields have been mutually helpful. 



Mohl, in his treatise on the vegetable cell, published in 1851, 

 gives the following account of protoplasm : " If a tissue composed 

 of young cells be left some time in alcohol, or treated with nitric or 

 muriatic acid, a very thin, finely granular membrane becomes de- 

 tached from the inside of the walls of the cells, in the form of a 

 closed vesicle, which becomes more or less contracted, and con- 

 sequently removes all the contents of the cell which are enclosed in 

 this vesicle from the wall of the cell. Reasons hereafter to be dis- 

 cussed have led me to call this inner cell the ' primordial utricle' 

 {priviordiahchlaticfi) . ... In the centre of the young cell, with 

 rare exceptions, lies the so-called nucleus cellulcE of Robert Brown 

 (' Zellenkern ;' ' Cyioblast' of Schleiden). . . . The remainder of 

 the cell is more or less densely filled with an opaque, viscid fluid of 

 a white color, having granules intermingled in it, which fluid I call 

 ' protoplasm.' " 



We must now pass without notice numerous contributions to the 

 subject, and consider Hofmeister's description of protoplasm given 

 in his " Vegetable Cell," published in 1867 : " The substance proto- 

 plasm, whose peculiar behavior initiates all new development, is 

 everywhere an essentially homogeneous body. It is a viscid fluid 

 containing much water, having parts easily motile, capable of 

 swelling, and possessing in a remarkable degree the properties of 

 a colloid. It is a mixture of different organic matters, among 

 which albuminoids and members of the dextrine group are always 

 present. It has the consistence of a more or less thick mucus, and 

 is not miscible with water to any great extent." 



From these accounts we see that the following points were re- 

 garded as established : i. All of the activities of the vegetable cell 

 are manifested in its protoplasmic contents ; 2. Protoplasm con- 

 sists chemically of a nitrogenous basis ; 3. Protoplasm has no 

 demonstrable structure ; 4. The protoplasmic contents in one vege- 

 table cell are not connected with the protoplasmic contents in 

 adjoining cells ; 5. The nucleus and other vitalized granules in the 

 vegetable cell are formed by differentiation from amorphous proto- 

 plasm. 



It is now our duty to see in what manner these views have been 

 modified during the last twenty, or rather ten, years. In describ- 

 ing the changes of opinion, time will not suffice for us to allude to 

 most of the observers : a few only can be mentioned by name. 



The first thesis, namely, that all of the activities of the vegetable 

 cell are manifested in its protoplasmic contents, may be regarded 

 as firmly established. It is at this point in our present examina- 

 tion when, if we had time, we should take up, one by one, the 

 terms which have been applied to some parts of what Mohl and 

 Hofmeister knew as protoplasm. But we can only glance at them 

 in passing. Thus, " cytoplasma " is understood to be the mass 

 exclusive of the granular contents of all kinds: " hyaloplasma " is 

 the outer hyaline layer ; " polioplasma " is the grayish granular 

 part. To these terms may be added others, such as " para- 

 plasma," etc. 



The second thesis, viz., protoplasm consists chemically of a 

 nitrogenous basis, remains unchanged. But, instead of regarding 

 the protoplasmic basis as comparatively simple, it is now known to 

 be exceedingly complex, and to contain numerous cognate proteids, 

 some of which can be identified in the basic mass, others in the 

 nucleus, and others still in the vitalized granules. 



These researches must be considered also with reference to those 

 by two active investigators, Pfef^er and De Vries. The former has 

 shown the conditions under which active protoplasm re-acts in the 

 presence of certain chemical excitants : the latter has demonstrated 

 the relations of a part of this irritability of protoplasm to its physi- 

 cal constitution. But, as a result of all these recent studies, it 

 becomes more and more clear that the chemical relations of the pro- 

 toplasmic activities are still veiled in mystery. Botanists are reced- 

 ing from a position held by many only a few years ago ; namely, 

 that it is safe to use the words " albuminoids " and " protoplasm " 

 interchangeably. Nowadays the latter term is generally restricted 

 to morphological and physiological conceptions : the former keeps 

 its wide chemical significance. 



Just here come in the chemical studies of protoplasm, — by 



