908 



SCIENCE. 



[N. S. Vol. V. No. 128. 



200 per minute ; the average number of 

 respirations at a temperature of 68° F., 72. 

 Both vagus nerves are inhibitory and ap- 

 parently equally so. They do not seem to 

 be in a state of tonic activity. Stimulation 

 of the central end of one vagus gives the 

 usual slight fall of blood pressure, with 

 slowing of the heart if the other nerve be 

 intact. Stimulation of the peripheral end 

 gives different results in different seasons 

 of the year. In the fall and early winter 

 months vagus excitation results in a gradual 

 and moderate slowing but never stoppage 

 of the heart, a gradual and moderate fall 

 of blood pressure, and on cessation of stim- 

 ulation a gradual return to the normal 

 rate and blood pressure. In the late 

 winter and spring months even with weak 

 stimulation the heart is easily and sud- 

 denly stopped and held at a standstill ; 

 the fall of blood pressure is sudden and 

 marked ; the rise of pressure is generally 

 sudden and often far above the normal, with 

 a following gradual fall below the normal 

 level. The tracings show considerable 

 irregularity. A marked depression in the 

 vitality of the animals v.^as noticed at this 

 time, which seems to be associated with the 

 seasons and to be of practical importance, 

 in view of the fact that guinea pigs are 

 used so largely in experimental pathology. 

 The heart ' escapes ' quickly from vagus 

 stimulation, but, on the whole, the latter 

 seems to be deleterious to cardiac action, 

 leaving the heart weaker and the blood 

 pressure lower than normal. After escape 

 from one vagus has commenced, stimula- 

 tion of the other usually brings the heart 

 to a standstill a second time. There is 

 some evidence that in the guinea pig there 

 is a separate depressor nerve, but further 

 work is necessary to make it conclusive. 

 Ending of Sensory Nerves in the Viscera with 

 special reference to such Endings in the Blad- 

 der. (Demonstration.) G. Carl Huber. 

 Gaskell, Langley and Edgeworth have 



described large medullated fibres in the 

 sympathetic system. These large fibres no 

 doubt come from the spinal and other sen- 

 sory ganglia. Kolliker suggests that some 

 of these fibres are destined to supply the 

 Pacinian corpuscles. The author has found 

 that the bladder of the frog is a most suita- 

 ble object for studying the free ending of 

 such sensory fibres. Large medullated 

 fibres, which could often be traced through 

 several small sympathetic ganglia, found 

 in the wall of the bladder, could then be 

 followed through their several branchings 

 until their terminal branches found between 

 the epithelial cells lining the bladder were 

 reached. A single nerve fibre was found 

 to innervate an area of about J.sq. mm. 

 These endings resemble very closely the 

 free sensory endings described for the mouth 

 and skin. 



The preparations were stained in methy- 

 lene blue and fixed in a solution of ammo- 

 nium picrate. They were then cleared in 

 a mixture of glycerine and ammonium 

 picrate, in which solution they were 

 mounted. 

 Endings of Sensory and Motor Nerves in the 



' Muscle Spindles ' of Voluntary Muscle with 



demonstration of preparations. G. C. Huber 



(with Mrs. De Witt). 



In 1860 Weismann described in embry- 

 onic striated muscle peculiar fibres with a 

 large number of nuclei. Similar structures 

 have been found widespread in vertebrate 

 muscle and have been called ' muscle spin- 

 dles. ' Their nature has been variously re- 

 garded. They contain muscle fibres within 

 a capsule and both motor and sensory 

 nerves go to them. 



The author has studied them in the frog, 

 snake, cat, dog, rabbit, rat and guinea f)ig. 

 The nerve fibres and endings were stained 

 in methylene blue. They were then cleared 

 in ammonium picrate and glycerine for 

 teasing, or were cut into sections and dou- 

 ble stained with alum carmine to bring out 



