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THE POPULAR SCIENCE MONTHLY 



change takes place throughout, making 

 every part more negative. The greatest 

 change is on the external surface of the 

 leaf, immediately opposite to the three sen- 

 sitive hairs. There is no relation between 

 the preexisting currents and the electrical 

 disturbance consequent on stimulation. The 

 period of latent stimulation (i. e., the space 

 of time occupied by the primary action of 

 the stimulus) is about one-sixth of a sec- 

 ond. The period during which the disturb- 

 ance lasts is about one second. As the 

 leaf becomes fatigued, the period of latency 

 increases to one second and three-quarters, 

 and then most likely the next stimulation 

 produces no effect. The change appears to 

 be a function of the protoplasm of the paren- 

 chyma of the region out of which the sensi- 

 tive hairs arise. Certain of the characters 

 of the change are similar to those presented 

 by muscle and nerve. Why the variation 

 should be a negative one, Dr. Sanderson is 

 unable to determine. 



New Shells from Colorado. In the 



extensive and remarkable display of nat- 

 ural-history objects brought to the Centen- 

 nial Exhibition by Mrs. M. H. Maxwell, of 

 Boulder, Colorado, was a box of land and 

 fresh-water shells. These have been ex- 

 amined by Mr. Ernest Ingersoll, who made 

 careful studies of the Rocky Mountain mol- 

 lusks in connection with the United States 

 Geological Survey in 1874, and summarized 

 his results in an article printed in this 

 magazine for May, 1876. Boulder is at the 

 mouth of Boulder Cation, several miles 

 northeast of Denver, at an altitude of about 

 5,530 feet above the sea, and on the east- 

 ern slope of the main range, where hereto- 

 fore no shells had been found. The list 

 includes Zoniles arboreus, Z. fulvns, Patula 

 Cooperi (living, and very dark and fine), P. 

 striatella, Helix pulchella, Cionella subcylin- 



drica, Vertigo ? (very minute), Suc- 



cinea lincata, S. Nuttalliana, Lirnnea palus- 

 tris, L. desidiosa, L. humilis, Physa hetero- 

 stropha, P/anorbis bicarinatus, P. lumens, 

 Helisoma plexata, Gyranlus parvus, Ancy- 



lus ?, Goniabasis liveseens, G. pulchella, 



Sphcerium striatinum, Pis-idium abditum, 

 and an anodon hardly identifiable. 



The collection is remarkable, as coming 

 from the eastern slope of the range, and 



embracing some unexpected species from 

 east and west. As usual, the Physas are 

 Protean in form, and one can make half a 

 dozen "species" out of them, if disposed. 

 Some of them are well-marked " Inflata." 

 Both the planorbs are reported for the first 

 time from Colorado. P. bicarinatus is a 

 well-known Eastern shell ; P. lumens has 

 hitherto been supposed to be confined to 

 Northern Mexico and Southern California. 

 The Helisoma is a new form, discovered by 

 Mr. Ingersoll in an isolated mountain-lake 

 in the southern part of the State, and Mrs. 

 Maxwell finds it at Boulder in a similar sit- 

 uation. Both the Melanians and the Spha- 

 rium are additions to the fauna of the 

 State, and the Anodonta will probably 

 prove to be undescribed. Mrs. Maxwell 

 proposes to search still more carefully when 

 she returns, and further information on the 

 geographical distribution of our mollusks 

 in the mountainous territories may be ex- 

 pected from various other quarters where 

 research has been stimulated by the curious 

 results already brought out. Colorado seems 

 to be a meeting-ground for mollusks from 

 all directions, and is a promising field for 

 the collector and student. 



Marey's Experiments on the Action of 

 the Heart. Experiments made by Marey 

 show that a diminution of excitability and 

 a rise of temperature in the muscular tissue 

 of the heart invariably coincide with the 

 cardiac systole, while the opposite phe- 

 nomena are manifested during diastole. 

 The same author has recently attempted to 

 ascertain whether any corresponding varia- 

 tions of the cardiac muscle could be made 

 out. The galvanometer, owing to the iner- 

 tia of its needle, is unsuitable for the obser- 

 vation of sudden changes in the intensity 

 of currents. Hence, in Marey's experi- 

 ments, Lippmann's electrometer was em- 

 ployed. The heart of a frog was placed on 

 two unpolarizable electrodes, one support- 

 ing the apex of the ventricle, while the 

 auricles rested on the other. Two succes- 

 sive negative variations of the current were 

 indicated by the electrometer during each 

 cardiac systole ; one of these was sudden, 

 and corresponded with the abrupt contrac- 

 tion of the auricles ; the other was more 

 gradual, and coincided with the slower 



