610 REPORT — 1889. 



MicellcB and Tagmata (Ndgeli, Pfeffer"). 



I have trought you to this point as the outcome of what we know as to the 

 essential nature of the all-important relation between oxygen and life. In botanical 

 physiology the general notion of a stable catalysing framework, and of an inter- 

 stitial labile material, which might be called catalyte, has been arrived at on quite 

 other grounds. This notion is represented in plant physiology by two words, both 

 of which correspond in meaning — Micellse, the word devised by Nageli,and the better 

 word, Tagmata, substituted for it by Pfeifer. Nageli's word has been adopted by 

 Professor Sachs as the expression of bis own thought in relation to the ultra- 

 microscopical structure of the protoplasm of the plant cell. His view is that 

 certain well-known properties of organised bodies require for their explanation the 

 admission that the simplest visible structure is itself made up of an arrangement of 

 units of a far inferior order of minuteness. It is these hypothetical units that 

 Nageli has called Micellae. 



Now, Nageli ^ in the first instance confounded the micellae with molecules, con- 

 ceiving that the molecule of living matter must be of enormous size. But, 

 inasmuch as we have no reason for believing that any form of living material is 

 chemically homogeneous, it was soon recognised, perhaps first by Pfeffer,^ but 

 eventually also by Nageli himself, that a micella, the ultimate element of living 

 material, is not equivalent to a molecule, however big or complex, but must rather 

 be an arrangement or phalanx of molecules of dififerent kinds. Hence the word 

 Tagma, first used by Pfeffer, has come to be accepted as best expressing the notion. 

 And here it must be noted that each of the physiologists to whom reference has 

 been made regards the micellae, not as a mere aggregate of separate particles, but 

 as connected together so as to form a system — a conception which is in harmony 

 with the view I gave you just now from the side of animal physiology, of catalysing 

 framework and interstitial catalysable material. 



To Professor Sachs, this porous constitution of protoplasm serves to explain the 

 property of vital turgescence, that is, its power of charging itself with aqueous 

 liquid — a power which Sachs estimates to be so enormous that living protoplasm 

 may, he believes, be able to condense water which it takes into its interstices, to 

 less than its normal volume. For our present purpose it is sufficient for us to 

 understand that to the greatest botanical thinkers, as well as to the greatest animal 

 physiologists, the iiltimate mechanism by which life is carried on is not, as Professor 

 Sachs ' puts it, ' slime,' but ' a very distensible and exceedingly fine network.' 



Ino-tagmata (^Engelmann, Pfliiger, Bernstein). 



And now let us try to get a step further by crossing back in thought from plants 

 t« animals. At first sight, the elementary vital processes of life seem more com- 

 plicated in the animal than in the plant, but they are, on the contrary, simpler ; 

 for plant protoplasm, though it may be structurally homogeneous, is dynamically 

 polyergic — it has many endowments — whereas in the animal organism there are 

 cases in which a structure has only one function assigned to it. Of this the best 

 examples are to be found among so-called excitable tissues, viz. those which are 

 diS'erentiated for the purpose of producing (along with heat) mechanical work, 

 light, or electricity. In the life of the plant these endowments, if enjoyed at all, 

 are enjoyed in common with others. 



By the study, therefore, of muscle, of light organ and of electrical organ, the 

 vital mechanism is more accessible than by any other portal. About light organs 

 we as yet know little, but the little we know is of value. Of electrical organs 

 rather more, about muscle a great deal. 



To the case of muscle, Engelmann, one of the best observers and thinkers on 

 the elementary questions which we have now before us, has transferred the 



• Nageli, ' Theorie der Gahrung,' Beitrafi zur Molecular Physiologic, 1879, p. 121. 

 ^ Pfeffer, PJiamenphysioloffie, Leipsic, 1881, p. 12. 



' Sachs, Expeiimental-Physiologie, 1865, p. 443; and Lectures on tlie Physiology of 

 Plants, English translation, p. 206, 



