May, igo6.J 



KNOWLEDGE & SCIENTIFIC NEWS. 



427 



protoplasm must be looked upon as being a substance 

 of extremely unstable constitution, such, indeed, that 

 the slightest stimulus will cause an immediate kata- 

 bolic followed by a rapid anabolic change, both of these 

 being an increase of the usual metabolic changes. This 

 change is capable of being transmitted from cell to cell 

 by means of the protoplasmic connecting strands, and 

 it is thus that we are able e\en in plants to explain the 

 transmission of stimuli from one part to another of the 

 same organism. 



The anabolic change is to be looked upon as a process 

 tending towards repair, but the protoplasm remains in 

 the same unstable equilibrium as before. 



Protoplasm that has been killed has passed into a 

 state of stable chemical and physical constitution, and 

 has undergone a complete change with regard to the 

 arrangement of its indi\idual molecules; in fact, it is 

 the very instability of living protoplasm that endows it 

 with its peculiar property of responding at once to 

 stimuli. Protoplasm once dead is open to the ordinary 

 processes of chemical decomposition, but on account of 

 the stable arrangement of its molecules is no longer 

 capable of responding to external stimuli. One of the 

 most important conditions for the retention of irritability 

 is the presence of oxygen, whereby metabolic changes 

 can proceed; and the presence of water both in combina- 

 tion with the protoplasm and otherwise is essential, all 

 living protoplasm having some " water of constitution " 

 which is present in the protoplasm of the driest seeds. 

 Naturally, in living protoplasm, anabolic and katabolic 

 changes are always proceeding to a certain extent, and 

 when above we mentioned the rapid succession of these 

 processes as being one of the essential concomitants in 

 the reaction of protoplasm to stimuli, it was meant that 

 these processes occur then with greater intensity and in 

 regular alternation. A " Current of Rest " is always 

 present in living protoplasm, but when a stimulus is 

 given to it, anabolism and katabolism proceed with a 

 fixed period of alternation, and with greater intensity 

 than before, giving rise to an increased current or " cur- 

 rent of action " — very similar to what happens when a 

 muscle passes from a state of rest into one of contraciion. 



In fact, a close analogy might he drawn between a 

 muscle and a cell; a muscle responds to a stimulus by 

 contracting, and during this contraction certain electri- 

 cal changes take place, metabolism is increased, and 

 heat is produced; the protoplasm of a cell responds to 

 stimuli by, perhaps, some aJteration in shape, or in 

 some cases by more rapid movement round a cell cavitv, 

 and during this metabolism is increased ;ind electrical 

 changes take place. But in both cases it is probably 

 the more rapid succession of the metabolic changes, 

 consequent on the stimulus, that is the cau.sc of the 

 outward manifestation; as to the alteration in the physi- 

 cal arrangement of the molecules, this is as yet un- 

 determined, but, with the increa.se in scientific know- 

 ledge, will no doubt be <\plaincd at .1 later date. 



The Chemistry of 

 Proteids. 



Rare Elements.— .\ revised table has been compiled bv 

 Mr. E. L. N. .\rmbrecht, and is published by Messrs. .^rmbrecht', 

 Nelso.i & Co, of the Rare Elements. The table, which is of 

 considerable interest as well as of great utility, gives the symbol, 

 specihc gravity, atom's weight, principal source, and chief 

 prope.-ties of each of some seventy of the rare elements. The 

 nam^ of the discoverer and in some cases the name of the chemist 

 who first isolated the metal or element is also added ; and, by no 

 means least in importance or interest, the market price of the 

 element is furnislied. I'rom this it appears that, subject to the 

 natural fluctuations. Yttrium, Vanadium. Thorium, Tantalium, 

 Rutlieniura, Rubidium. Rhodium, Niobium, Lanthanum, Iridium, 

 Indium, Erbium, Beryllium and Barium are the chief of the rare 

 eleme Us which are worth upwards of a shilling a grain. 



By Ida Smedley, D.Sc. 



Of the three great classes of substances which form 

 the chief products of animal metabolism — fats, carbo- 

 hydrates and proteids — the last-named have for long 

 withstood all efforts to determine the nature of their 

 constitution. Although this problem has occupied the 

 attention of more workers than almost any other group 

 of substances, it is only within the last five years, chiefly 

 owing to the brilliant work of Emil Fischer and his 

 pupils, that we are in a position to form some definite 

 conception of the nature of their atomic structure. The 

 steps made in this direction have so far only led us to 

 the synthesis of peptides, substances of much smaller 

 molecular size than the native proteids, bearing, how- 

 ever, considerable resemblance to them, and occurring 

 among their cleavage products. Such syntheses may 

 probably be regarded as analogous to those of the 

 simple hexose sugars, the structure of starch and of 

 the more complex carbohydrate molecules remaining 

 unsolved. 



The earlier investigators were very largely concerned 

 with the isolation and classification of individual pro- 

 teids; the latter based mainly on differences in two 

 physical properties, temperature of coagulation and 

 solubility in the presence of inorganic salts. Unfor- 

 tunately in dealing with these colloidal substances, the 

 identification of chemical individuals presents great 

 difficulties, the properties relied on in classification be- 

 ing those which would be readily affected by the pre- 

 sence of impurities. It has recently been shown that 

 members of two of the most sharply differentiated of 

 these classes, the albumins and globulins, under certain 

 conditions suffer mutual conxersion. A more satisfac- 

 tory scheme of classification will probably be based on 

 differences in their chemical structure, but for this, a 

 knowledge of their decomposition products and the pro- 

 portions in which they are present, more complete than 

 we at present possess, will be necessary. 



The colour reactions given by the proteids when 

 treated with various reagents were also investigated, 

 and some attempt made to allocate the groups in the 

 molecule characteristic of special reactions; in this field 

 our knowledge, though recently considerably extended, 

 is still far from complete. 



A study of the gradual decomposition of proteids by 

 hydrolysing agents, both acids and enzymes, resulted in 

 the separation and classification of the non-crystalline 

 derivatives of digestion, aJbumoses, and peptones, and 

 also in the isolation of a number of crystalline amiiio- 

 acids, the best characterised being leucin and tyrosin. 

 In the recent extension of our knowledge of these 

 simpler decomposition products, the work of Kossel and 

 of Emil Fischer stands pre-eminent; the former isolated 

 ■his so-called " hexone bases " arginine, lysine, and 

 histidine, the constitution of all of which has now been 

 definitely established. To Emil I>"ischer we arc indebted 

 both for the isolation of new compounds and for 

 definitely establishing the constitution of products w hich 

 former inve.stigators had only succeeded in separating. 

 The problem of the structure of proteids mav be at- 

 tacked both by analytical and synthetical methods, the 

 latter being dependent on the former, since the simple 

 decomposition products isolated will aiTord a clue as to 

 the materials to be employed in synthesis. Now, although 



