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THE POPULAR SCIENCE MONTHLY. 



I infer that the theory of acetonsemia is 

 founded on good evidence." Dr. Richard- 

 son mentions also the secondary absorption 

 of poisonous matter from wounds, and from 

 the abraded and ulcerating surfaces pro- 

 duced in diphtheria, malignant scarlet fever, 

 etc., and concludes by saying : " Such ob- 

 servations as have been noticed under this 

 short head lead to a study of another new 

 point, namely, the possibility of the forma- 

 tion of organic alkaloids in the body during 

 some conditions of disease. Scientific dis- 

 covery has not, however, advanced so far as 

 to enable me at this moment to do more 

 than allude to one of the newest and most 

 important studies in modern medical re- 

 search." 



Meebanism of Plant-Contraction. — Dr. 



J. Burdon-Sanderson, in a lecture before 

 the Royal Institution of Great Britain, per- 

 formed an experimental demonstration of 

 the causes and phenomena of the excitabil- 

 ity of plants. The number of plants which 

 exhibit what is often called irritability is 

 very considerable, but the illustrations of 

 the lecture were drawn chiefly from typical 

 specimens of only a few of the most fa- 

 miliar kinds, such as mimosa, dionea, and 

 two or three others. The mimosa pre- 

 sents nearly the same appearance when 

 asleep as when excited, but is then liable 

 to a further change, by the operation of 

 which it sinks to a still lower position and 

 becomes Ump. The excitatory effect is 

 dependent on a vital change in the proto- 

 plasm of the cells, which may be observed 

 when the plant is asleep as well as when 

 it is awake. The cells of the plant, which 

 unexcited are distended or charged with 

 liquid, undergo on excitation a sudden dimi- 

 nution of tension or of expansion by the 

 discharge of the water contained in them, 

 which finds its way first into the intercel- 

 lular air-spaces, and then out of the motor 

 organ altogether. The discharge is due to 

 a sudden loss of its water-absorbing power 

 by the protoplasm of the cell, whereby the 

 external cell-sac, whose elastic tendency to 

 contract is kept in check only by the con- 

 stantly distending action of the protoplasm^ 

 presses upon it with force enough to squeeze 

 out the cell-contents. This action being par- 

 ticipated in by all the individual cells, the 



leaf -stalk, or whatever organ it may be that 

 droops, necessarily becomes limp and .falls. 

 The motion of the leaf is, however "the 

 result of the action of many hundred in- 

 dependent cells, all of which may act to- 

 gether, but may not. In either case they 

 take a great deal longer to think about it ; 

 for during a period after excitation, which 

 amounts at ordinary summer temperature 

 to about a second, the leaf remains abso- 

 lutely motionless." During this interval an 

 electrical disturbance takes place in the 

 plant, the character and operation of which 

 were neatly shown by the aid of some 

 extremely delicate apparatus. Obvious and 

 well-marked differences were pointed out 

 between the mechanism of plant motion 

 and that of animal motion ; but the differ- 

 ences are not essential, for they depend 

 not on difference of quality between the 

 fundamental chemical processes of plant 

 and animal protoplasm, but merely on dif- 

 ferences of rate or intensity. "Both in 

 the plant and in the animal, work springs 

 out of the chemical transformation of mate- 

 rial, but in the plant the process is rela- 

 tively so slow that it must necessarily store 

 up energy, not in the form of chemical 

 compounds capable of producing work by 

 their disintegration, but in the mechanical 

 tension of elastic membranes. The plant- 

 cell uses its material continually in tighten- 

 ing springs which it has the power of let- 

 ting off at any required moment by virtue 

 of that wonderful property of excitability 

 which we have been studying. Animal con- 

 tractile protoplasm, and particularly that 

 of muscle, does work only when required, 

 and, in doing so, uses its material directly." 



Origin of Winding River-Beds.— Major 



Stevanovics, a Hungarian oflScer, has pub- 

 lished an essay on the laws by which the 

 " wash " and meandering of rivers are regu- 

 lated. Based on studies of the Theiss and 

 the Danube, the principles he elucidates are 

 illustrated in the windings of rivers the 

 world over, with such variations only as dif- 

 ferences in situations and exposures might 

 occasion. The deviations which rivers are 

 constantly making in their course are, it 

 appears, determined by fixed laws, which 

 engineers should be competent to find out 

 and regard. To understand them more fully, 



