ArKlL 6, 1SS3.] 



SCIENCE. 



247 



sinus, it seems pretty certain that the systoles of that 

 part are also primarily due t(5 its muscular tissue, 

 and not to the nerve-cells in it. Recent researches 

 seem to show that all contractile tissue has primi- 

 tively a tendency to contract rhythmically; and we 

 may perhaps regard the phenomena above described 

 as due to a greater retention of this property in the 

 muscle-fibres of the venous sinus of the tortoise- 

 heart, as compared with those of the ventricles, AA'liich 

 have lieen so modified for the purpose of rapid and 

 powerful contraction as to interfere with the mani- 

 festation of the fundamentally inherent tendency to 

 exhibit so-called spontaneous riiytlnnical beats. 



The concluding portion of Gaskell's paper is con- 

 cerned with the action of a weak, interrupted cur- 

 rent upon certain functions of the cardiac muscle, 

 and its resemblance to the action of the vagus nerve. 

 He had already proved, so far as the frog is con- 

 cerned, that stimulation of the vagus might, imder 

 various circumstances, produce directly opposite re- 

 sults, which may be arranged in paii's. It may cause, 

 1°, Slowing or acceleration of the rhythm; 2°, 

 Diminution or increase of the force of the contrac- 

 tions; 3°, Diminution or (possibly) increase of tone. 

 From subsequent work with the tortoise-heart, he 

 now adds, 4°, Diminution or increase of conductivity 

 in the cardiac muscle. As a corollary to the latter, 

 is to be added the influence of vagus stimulation 

 upon sequence of beats in the successive heart-cavi- 

 ties. When an artificial hindrance to conduction in 

 the cardiac muscle (as by clamping) is intei-posed, 

 vagus stimulation may either entirely check the trans- 

 mission of the wave of contraction, or may facilitate 

 it; and similarly it may shorten or lengthen the time- 

 intervals between the conti-actions of successive 

 heart- chambers. The initial effect of vagus stimu- 

 lation is often to depress some function : its final and 

 most enduring power is to exalt, intensify, and re- 

 pair that function. It slows rhythm, but its stimu- 

 lation makes rhythmic beats last longer than they 

 otherwise would. It diminishes at first the force of 

 the contractions, but its ultimate effect is to improve 

 and sustain the contractile force. It may primarily 

 diminish conductive power, yet in the end it com- 

 pletely restores that power. Gaskell concludes that 

 the vagus is essentially the trophic nerve of the heart. 



All the above results of vagus stimulation are re- 

 peated exactly when an interrupted cm'rent not pow- 

 erful enough to cause contractions is sent through 

 an isolated strip of the apex of the ventricle of the 

 heart of the tortoise. Further: atropine applied to 

 this strip prevents the action of the interrupted cur- 

 rent upon it. Just as this drug prevents the action of 

 the vagus upon the Avhole "heart. Since the strip 

 contains no nerve-cells, the interrupted current must 

 act directly upon the muscular tissue. Hence it is 

 ■made probable that the vagus nerve also immediately 

 influences the cardiac muscle without any necessary 

 intervention of nerve-cells ; and also that atropine 

 exerts its well-known influence upon the heart, not, 

 as has hitherto been generally assumed, by acting 

 upon the ganglia in that organ, but by immediately 

 influencing the properties of its muscular tissue. 



H. Newell Martin. 



by the burning of coal for heating and manufacturing 

 purposes, can affect the temperature of the air an 

 appreciable amount, will be seen to l)e hardly tenable 

 when it is considered that a breeze of five to ten miles 

 per hour (which is a very light one) will entirely re- 

 move the air in the city each hour; that the number 

 of flues by which the heated air is carried out is ex- 

 ceedingly small as compared with the whole atmos- 

 phere over the city; lastly, that reliable observations 

 taken in the city and adjacent country show that no 

 such effect is noticeable. Of the last, any one can 

 satisfy himself by consulting observations made in 

 Central-Park observatory and the Signal-office in 

 New- York City. Both of tliese observatories are 

 fitted up with the very best instruments, and the 

 records may be regarded as reliable as any in the 

 country. The observations for ISTS for the first- 

 named station have been published in the annual re- 

 port of the New-York meteorological observatory, 

 and, for the second station, in the reports of the chief 

 signal-officer for 1878 and 1879. The following figures 

 show maximum and minimum temperatures for each 

 month of 1878 : — 



THERMOMETER EXPOSURE. ' 



Some may have been misled by a note on ther- 

 mometer exposures of the signal-service, which ap- 

 peared on p. 156 of Science. The subject is by no 

 means so simple as that note would seem to indicate. 

 Eesults of temperatures observed in the same neigh- 

 borhood vary greatly. That the heat of a city, caused 



When it is considered that these stations are in 

 such diverse surroundings, with different exposures 

 of instruments, and widely different positions as 

 respects the sea, the above agreements can but appear 

 very remarkable. Abundant similar facts may be 

 easily found. Undoubtedly there are great differ- 

 ences of temperature in the same city or village, due 

 to currents of cold air coming down valleys, differ- 

 ences of exposure of instruments, proximity to large 

 bodies of water, and innumerable other causes ex- 

 ceedingly difficult to guard against. If any one has a 

 doubt as to the uniform results obtained by the signal- 

 service, a glance at the weather-map any day will con- 

 vince him that isotherms can readily be drawn by using 

 the observations made by the service. If it be claimed 

 that these temperatures on the Atlantic seaboard are 

 too high, it will, at the same time, be seen that this 

 is due in large measure to the proximity of the 

 cities to the sea; and it is necessary to establish the 

 stations there to meet the needs of seafaring men. 

 Experiments are being carried on in England in order 

 to determine the proper manner of exposure of ther- 

 mometers. Certainly the continental method of pla- 

 cing thermometers at four feet from the ground will 

 hardly give proper temperatures in the spring and 

 autumn in the northern United States so long as there 

 is snow on the ground. What are needed are definite 

 results from careful observations, and not indefinite 

 or general expressions. 



