Chap. XIII.] TRANSMISSION OF MOTOR IMPULSE. 255 



have been overlooked, as I made thin vertical sections of the 

 leaf at the bases of the filaments. 



On several occasions, slits about the iV of an inch in 

 length were made with a lancet, close to the bases of the 

 filaments, parallel to the midrib, and, therefore, directly 

 across the course of the vessels. These were made sometimes 

 on the inner and sometimes on the outer side of the fila- 

 ments; and after several days, when the leaves had re- 

 opened, these filaments were touched roughly (for they were 

 always rendered in some degree torpid by the operation), and 

 the lobes then closed in the ordinary manner, though slowly, 

 and sometimes not until after a considerable interval of 

 time. These cases show that the motor impulse is not trans- 

 mitted along the vessels, and they further show that there 

 is not necessity for a direct line of communication from the 

 filament which is touched towards the midrib and opposite 

 lobe, or towards the outer parts of the same lobe. 



Two slits near each other, both parallel to the midrib, 

 were next made in the same manner as before, one on each 

 side of the base of a filament, on five distinct leaves, so that 

 a little slip bearing a filament was connected with the rest 

 of the leaf only at its two ends. These slips were nearly of 

 the same size; one was carefully measured; it was .12 of an 

 inch (3.048 mm.) in length, and .08 of an inch (2.032 mm.) 

 in breadth; and in the middle stood the filament. Only one 

 of these slips withered and perished. After the leaf had 

 recovered from the operation, though the slits were still open, 

 the filaments thus circumstanced were roughly touched, and 

 both lobes, or one alone, slowly closed. In two instances 

 touching the filament produced no effect; but when the 

 point of a needle was driven into the slip at the base of the 

 filament, the lobes slowly closed. Now in these cases the 

 impulse must have proceeded along the slip in a line par- 

 allel to the midrib, and then have radiated forth, either from 

 both ends or from one end alone of the slip, over the whole 

 surface of the two lobes. 



Again, two parallel slits, like the former ones, were made, 

 one on each side of the base of a filament, at right angles to 

 the midrib. After the leaves (two in number) had recovered, 

 the filaments were roughly touched, and the lobes slowly 

 closed ; and here the impulse must have travelled for a short 



