June lo, 1880] 



NATURE 



^Z1 



first are true parasites, the mycelium of which, living on the 

 tissues of the host, frequently kills it ; the second are false 

 parasites (saprophytes), deriving their nourishment from vege- 

 table substances in various stages of decomposition. The genus 

 Polyponis he considers to belong to the first, Agaricus to the 

 second of these classes. The common disease of the mulberry - 

 tree he attributes to Polyporus mori, not to Agaricus milieus, as 

 suggested by Piccone. — A. Mori discusses the old statement of 

 Gasparrini, recently revived by Licopoli, that beneath the 

 stomata of the leaves are cavities, to which Gasparrini gave the 

 name clsloma, which are clothed by a continuation of the cuticle. 

 HLs observations do not lead him to confirm this statement, but 

 rather to the conclusion that the walls of the cavity beneath the 

 stoma consist of ordinaiy cellulose. 



In the number of the Scottish Naturalist for April is the com- 

 mencement of a suggestive article by the Rev. A. Milroy on the 

 value of the names of places in indicating the ancient surface- 

 features of the country. He takes as an example the country on 

 the banks of the Tay below Perth, and shows the light that is 

 thrown by the Saxon and Celtic local names, not only on the 

 ethnological histoiy of the district,' but also on the changes 

 which have taken place in its physical features. 



The American Naturalist, May, contains ; — Eduard Burgess, 

 the structure and action of a butterfly's trunk. — J. S. Lippincott, 

 the critics of evolution. — E. H. Varnall, Hall's second Arctic 

 expedition. — O. T. Mason, sketch of North American anthropo- 

 logy in 1879. — The editor's table, on the Academy of Natural 

 Sciences, I'hiladelphia. — On the proposed exploration of the 

 ruins of Mexico and Central America — Recent literature. — 

 General notes. — Scientific news. 



Journal of the Franklin Institute, May. — Naval architecture, 

 by Mr. Haswell. — Table and diagram for determining the 

 diameters of speed cones when connected by an open belt of 

 constant length, by Mr. Klein. — Experiments with a steam 

 cutter, by Mr. Ishervvood. — Eye memory, by Mr. Leiand. 



SOCIETIES AND ACADEMIES 

 London 



Royal Society, May 13. — " Notice of Further Experimental 

 Researches on the Time Relations of the Excitatory Process in 

 the Ventricle of the Heart of the Frog," by J. Burdou Sander- 

 son, M.D., and F. J. M. Page, B.Sc. 



The present paper is a continuation of one previously published 

 by the authors {Roy. Soc. Proc., xxvii. 410). The excitatory 

 state, i.e., the condition produced in any excitable structure, 

 vegetable or animal, by excitation, is characterised (i) by the 

 appearance of electromotive properties in the excited part which 

 did not exist before excitation and cease to exist as soon as its 

 effect is over ; (2) by diminished excitability ; (3) by the fact that 

 it is propagated from the part first excited to contiguous parts at 

 a rate which is different in different structures and in the same 

 structure at different temperatures. These three conditions are 

 important as being the only characteristics by which the hidden 

 process of excitation constantly reveals itself. By means of the 

 rheotome described by one of the authors, exact measurements 

 have been made of the time relations of the above conditions. 

 The results obtained by Engelmann {Pfliig. Arch., xvii. 68) are 

 then discussed. In forty-seven out of seventy-eight preparations 

 of the ventricle of the frog made by this observer, the leading- 

 off contact nearest the point of excitation became first negative, 

 then positive to the other leading-off contact ; in the remaining 

 thirty-one the positive deflection was absent. In the case 

 in which the deflection was of a double character (Doppel- 

 schwankung), the first phase began o"'o6 after excitation, 

 and rapidly attained its maximum ; the reversal of sign took 

 place at o"'26, and the contacts became equipotential at 

 o''5. He estimated the rate of propagation at 50 mm. per 

 second. It will be noticed that these researches of Engel- 

 mann refer exclusively to the first half second after excitation, 

 and therefore correspond to what has been termed by the 

 authors of the present paper "the initial phase," and that the 

 "terminal phase" escaped the notice of Engelmann. The 

 method employed in the investigation of the above phenomena, 

 with the aid of the rheotome, is then briefly described. The 

 heart was carefully maintained at a'constant temperatiu'e by being 

 placed on a lacquered brass box, through which flowed a stream 

 of water at the desired temperature. The following table gives 



Time after excitation, at"\ 

 which galvanometric cir- ( 

 cuit was opened, the period | 

 of closure being o"'i ...) 

 Deflections 



Time after excitation, at' 

 which galvanometric cir- 

 cuit was opened, the period 

 of closure being o"'i ...; 

 Deflections 



-1-3 



+30,-1-' 



the results obtained in a typical experiment at 10' C, with the 

 ventricle of the frog. The preparation was led off at apex and 

 base, and excited close to the apex. The deflections represent 

 the relative]changes of potential at the apex contact. The authors 

 reiterate the statement contained in their previous paper, that the 

 electrical effect of excitation manifests itself in two phases, an 

 initial and a terminal one, which have opposite signs, and further 

 conclude that these two phases are separated by a relatively pro- 

 longed state of equipotentiality of the two apex contacts. These 

 statements agree with those of Engelmann as far as they relate 

 to the same period ; but as the whole of the jshenomena recorded 

 by him belong to the beginning of the first second, the com- 

 mencement of the period of equipotentiality is regarded by him 

 as the end of the excitatory effect ; but to the authors the absence 

 of galvanometric effect during this isoelectrical interval is the 

 expression of the fact that both contacts are in the same degree 

 of excitation. The proof that this period of equipotentiality is 

 one of balanced activities is obtained by subjecting the two 

 led-off surfaces to different temperatures. If the apex be warmed 

 the deflections of the terminal phase are'increased, and commence 

 at an earlier period ; if the apex be cooled they are diminished. 

 This is illustrated by the following table : — 



Slight injuries, such as those produced by an application of a 

 minute quantity of 10 per cent, salt-solution, resemble those 

 effected by slight warming. If the injury is more complete, such 

 as is produced by touching the surface momentarily by a red 

 hot wire, the isoelectrical interval is as it were filled up ; large 

 deflections in which the warmed surface appears to be positive 

 being obtained throughout the whole of the excitatory period 

 excepting the first tenth. This is seen in the following table : — 



As regards the period of diminished excitability, the experi- 

 ments of Marey (" Physiol. Exp." ii. 1S76, 85) are first discussed, 

 some experiments are then given which establish— (i) That the 

 duration of the period of diminished excitability agrees pretty 

 closely with that of electrical activity, and (2) that it is similarly 

 affected by changes of temperature. 



The rate of propagation of the excitatory wave in a fresh 

 preparation is about 130 mm. per second. 



Tlie facts above stated are consiistent with the foUowmg 

 theories :— l. Every excited part is negative to eveiy unexcited 

 part so long as the state of excitation lasts. 2. The local duration 

 of the excitatory state, i.e. the time it lasts in each structural 

 element, is measured by the time interval between the beginnnig 

 of the initial and the beginning of the terminal phase of the 

 variation. 3. When both contacts are at the same temperature 

 and in all other respects under the same conditions, the local 

 duration of tlie excitatory state is the same at both, consequently 

 it begins and ends earlier at the leading off contact first excited 

 than°at the other, the initial and terminal difterences expressing 



