660 



PHYSIOLOGY. 



physiological effects when introduced directly 

 into the blood, even in large quantities. They 

 do not apparently affect any part of the nerv- 

 ous system, but kill either by paralyzing the 

 heart, or by their action on the raucous mem- 

 brane of the lungs. When injected into the 

 arteries they have no action on the vaso-motor 

 centers or on the vagus. With these elements, 

 the toxic intensity is no longer a function of 

 the atomic weight. 



Sulphur and selenium, introduced into the 

 arteries, arrest respiration by their action on 

 the nervous system, and increase the irrita- 

 bility of the heart. Selenic acid is more poison- 

 ous than sulphuric. 



The physiological action of the group con- 

 sisting of chlorine, bromine, and iodine is well 

 marked. All of the members act on the vaso- 

 raotor and respiratory centers, and keep up 

 the irritability of the heart. Injection into the 

 arteries is followed by a great increase in blood- 

 pressure. The action on the respiratory cen- 

 ters is shown by a sudden suspension of respi- 

 ration in a general clonic spasm. 



The influence of veratria on muscular con- 

 traction has been found by Lauder Brunton 

 and Cash to vary much with the tempera- 

 ture of the muscle experimented upon. Up 

 to a certain limit, heat increases the effect of 

 the drug; cold diminishes it. Exposure to 

 extremes of heat or cold not sufficient to kill 

 the muscle prevents entirely the manifestation 

 of the usual symptoms of the presence of ve- 

 ratria. The observers remark that the modi- 

 fications in the action of this drug on muscle 

 occasioned by changes of temperature suggest 

 that temperature may modify the action of 

 other drugs, not only on muscle, but on nerves 

 and nerve-centers. Accordingly, the different 

 action of drugs on different animals, or on the 

 same animal in various physiological and patho- 

 logical conditions, may be due in part to dif- 

 ferences of temperature, either physiological 

 or pathological, within their organisms. 



Vegetable Physiology. Late investigations in 

 vegetable structure have brought out evidence 

 showing that the protoplasmic contents of the 

 cells of plants are not entirely shut off from 

 one another by the cell-walls, but that ar- 

 rangements exist of such a kind that more or 

 less delicate strands of protoplasm pass through 

 from one cell to another, piercing the cell- 

 walls either at numerous points where are 

 certain thinner spots, or simply here and 

 there. Th. Hartig, in 1837, distinguished cer- 

 tain constituents of the bast of phanerogams 

 which we now know as sieve-tubes. It has 

 since been established by the testimony of nu- 

 merous observers that strands or cords of proto- 

 plasmic substance pass through different pores 

 or passages in the septa or cell- walls. In 1880 

 Tangl discovered that, in the endosperm of 

 certain seeds, delicate filaments of protoplasm 

 traverse the cell-walls through fine perfora- 

 tions, and so place the protoplasmic contents 

 of the cells in direct continuity one with an- 



other. In 1882 Gardiner showed that a simi- 

 lar continuity of the protoplasm exists be- 

 tween the cells of the motile organs of certain 

 sensitive plants. Since 1882, Gardiner has 

 extended his results, and shown the existence 

 of a protoplasmic continuity through the cell- 

 walls of numerous other parts of plants, and 

 his researches have been confirmed by Rus- 

 sow ; so that there appears to be no reason 

 now why we should not accept generally the 

 view that the cells of plants are not closed 

 sacs, as was formerly believed, but are pro- 

 vided with passages penetrating their walls, 

 through which fine filaments of protoplasm 

 communicate. Other investigations throwing 

 light upon this matter from totally different 

 directions go to support the view first hinted 

 at by Hofmeister, and lately stated by Sachs, 

 that a much closer relation of cell to cell 

 exists than can be well explained by the the- 

 ory that a plant is a sort of cell-republic, 

 consisting of aggregated cell-units. It would 

 help the solution of the question raised at this 

 point to ascertain whether the continuity of 

 the protoplasmic strands is maintained from 

 the earliest stages, or is established later. If 

 the former view prevails, then the continuity 

 of the protoplasm through the wall of vegeta- 

 ble cells is simply to be regarded as an expres- 

 sion of the fact that the entire plant or organ 

 is practically one whole, or is one mass of pro- 

 toplasm, cut up into chambers which commu- 

 nicate with one another, and bounded by a 

 membrane on the exterior. If, on the other 

 hand, the communications between the proto- 

 plasm of neighboring cells are only established 

 after a complete septum has been formed, then 

 it may or may not be that that view will hold. 

 So far, the evidence on this point is not suffi- 

 cient to justify a general statement. 



The excitatory phenomena observed in cer- 

 tain plants have been studied by Dr. J. Bur- 

 don-Sanderson, who finds that they are de- 

 pendent on a vital change in the protoplasm 

 of the cells, and that this may be observed 

 when the plant is asleep as well as when it is 

 awake. The cells of the plant, which unex- 

 cited are distended or charged with liquid, un- 

 dergo on excitation a sudden diminution of 

 tension or of expansion by the discharge of 

 the water contained in them, which finds its 

 way, first into the intercellular 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 elasi it- 

 tendency to contract is kept in check only by 

 the constantly distending action of the proto- 

 plasm, presses upon it with force enough to 

 squeeze out the cell-contents. This action be- 

 ing participated 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 independent 

 cells, all of which may act together, or may not, 



