148 



NATURE 



[April 10. 19 13 



in the subdivision of the Centrechinoida (olim 

 Diademoida). Here the characters of the jaws are 

 used as the guiding features in the separation of three 

 suborders. 



The final part of the paper gives a complete survey 

 of all Palaeozoic Echinoids hitherto described, and, 

 naturally, includes the description of several new 

 genera and species. The completeness of the revision 

 may be gauged from the fact that figures are given of 

 all but four of the known species. The seventy-six 

 plates accompanying the paper are partly photographic 

 and partly diagrammatic, both alike admirably clear. 

 A full bibliography and an adequate index bring to a 

 fitting conclusion a work that must always remain a 

 classic to echinologists, and a model to workers on 

 other groups. H. L. H. 



CHEMISTRY OF THE SUGARS. 



PROF. EM1L FISCHER'S latest paper in the final 

 part of the Berlin Berichte for 19 12 brings 

 another chapter in the chemistry of the sugars to a 

 close. His welcome return to the subject has been 

 attended with the same brilliant experimental dexterity 

 which led to his former successes in this remarkable 

 group of compounds, and it is to be hoped that he 

 will yet succeed in conquering the still unsolved 

 problem of the synthesis of the disaccharides. Fischer 

 now describes the conversion of ordinary glucose into a 

 methyl pentose, and is enabled to clear up the con- 

 stitutional formula; of the stereoisomeric methyl pen- 

 toses and effect their complete synthesis from the 

 elements. 



The methyl pentoses are a somewhat remarkable 

 crroup of compounds ; they represent sugars of the type 

 of glucose in which one' hvdroxvl group is reduced so 

 that CH..OH is replaced by CH,. At first their 

 occurrence was rare and limited to a few coloured 

 glucosides. Many more of these have been described 

 recently, but the group is most widely represented 

 amongst the seaweeds, the investigation of which 

 we owe to Votocek. As a result of his work, several 

 isomerides of rhamnose, the methyl pentose which 

 was first discovered, are known. 



Fischer started from a dibromo-derivative of glucose, 

 discovered by Fischer and Armstrong ten years pre- 

 viously. The one bromine atom in this sub- 

 stance is attached to the carbon atom at 

 one end of the chain of carbons which con- 

 stitutes the skeleton of glucose; it is easily replaced 

 by methoxyl and a glucosidic compound formed. The 

 position of the second bromine was uncertain ; there 

 were reasons for considering it as attached to the 

 other end of the chain. This position is now con- 

 firmed by the fact that when the bromine atom is 

 reduced the glucoside of a methyl pentose is formed 

 from which the methyl pentose is in turn obtained. 

 The new sugar proves to be identical with a com- 

 pound described by Votocek, and receives the name 

 Isorhamnose. Its "configuration formula must be the 

 same as that of glucose, and it is easy to deduce the 

 formula of rhamnose and other members of the group. 



A side issue of the research, which, however, 

 possesses the very greatest interest, is the behaviour 

 of the new glucoside of isorhamnose towards enzymes. 

 Like the (3-methyl glucoside, from which it is derived, 

 it is hydrolysed by emulsin, though somewhat more 

 slowly.' Apparently the substitution of CH 3 for 

 CH,.OH is not sufficient to put the compound out of 

 harmonv with the enzyme; this is what might be 

 expected in view of Irvine's proof that tetramethyl-3- 

 methyl glucoside is likewise hydrolysed by emulsin. 

 It is "therefore all the more remarkable that 0-methyl 

 xvloside, which differs only in that the CH 3 group is 

 NO. 2267, VOL. 91] 



replaced by H, is not acted on by the enzyme in the 

 very least. 



A more striking proof of the selective nature of 

 enzyme action could not well be desired, and the 

 moment is opportune to emphasise this fact, since it 

 is fundamental to the interpretation of vital 

 phenomena. E. F. A. 



GYROSTATS AND GYRO STATIC ACTION J 



WE are accustomed in daily life to handle non- 

 rotating bodies, and their dynamical properties 

 excite little attention, though it cannot be said that 

 they are commonly understood. It is different, how- 

 ever, with rotating bodies. These, when handled, 

 seem to be endowed with paradoxical, almost magical 

 properties. I have here an egg-shaped piece of wood. 

 I place it on the table and it rests, as we expect it 

 to do, with its long axis horizontal. Our experience 

 tells us that this is the natural and correct position 

 of the body. But I set it spinning rapidly on the 

 table, as you see, with the long axis horizontal, and 

 you observe that after an apparently wobbling motion 

 it erects itself so that its long axis is vertical. It was 

 started spinning about a shortest axis, but the body 

 has of itself changed the spin, and it is now turning 

 about the long axis. In taking this position it has 

 actually raised itself against gravity, through a height 

 equal to half the difference between the lengths of the 

 long and short axes. This seems paradoxical, but 

 the man who is in the habit of spinning tops knows 

 that this is the proper position of the body, that it 

 must stand up in this way when spinning rapidly on 

 a rough horizontal plane. 



This experiment may be performed at the breakfast 

 table with an egg as the spinning body. But the egg 

 must be solid within — that is, it must be hard-boiled ; 

 a raw or soft-boiled egg will not spin. Perhaps this 

 was why Columbus did not adopt this method for his 

 celebrated experiment; there may, of course, have 

 been other reasons. 



It is thus made clear that by causing a body to 

 rotate rapidlv we endow it with new and strange 

 properties. Between a top when spinning and the 

 same top when not spinning there is a difference 

 which reminds us of that between living and dead 

 matter; and this will strike us still more forcibly 

 when we consider some more complicated cases of 

 rotational motion. The top, the ordinary spinning- 

 top of the schoolboy, stands on its peg and "sleeps" 

 in the upright position, in contempt of all the laws 

 which povern statical equilibrium. 



The experimental study of spinning-tops is carried 

 on by very small boys and a few more or less aged 

 people. Somehow, but I think quite wrongly, a top 

 is regarded as a toy suitable only for a child, and 

 that kind of amusement is scarcely encouraged by the 

 benevolent despots who so completely direct the games 

 of boys at school. Among older boys there used to be 

 a regular game in Scotland of " peeries," and some 

 of you mnv have read Clerk Maxwell's poetical de- 

 scription of the Homeric contests which distinguished 

 the sport. 



The ton as a plaything is depised; nevertheless it is 

 a most important contrivance. The earth on which 

 we live is a top, and a considerable range of astro- 

 nomical phenomena are most easily explained by refer- 

 ence to the behaviour of ordinary spinning-tops. It 

 is a ton that directs the dirigible torpedo, that controls 

 the monorail car. which may soon rise from the posi- 



1 Discourse deliver»d at the "oval Institution on Frichv. February 14. by 

 Prof. Andrew Grav, F.R S. Th- motor-gyro«tats described are the inven- 

 tion of Dr. T. H. Gray and Mr. C. B. Bttrnside. The fryrostatic tops and 

 combinations tised in the latter part of the lecture are due to Dr. Gray. 



