1890.] Physiology. 1087 
in the rabbit by touching, pressing upon, stroking, and heating points 
in the exposed articular surfaces of the tibia and metatarsus, an 
the deep-lying portions of the bones. Sensations indicated by 
respiratory reflexes were readily called out. The sensitiveness seems 
to lie not so much in the surface of the joint as in the layers beneath. 
No reaction was obtained from the hard bone itself, but the marrow was 
especially sensitive. 
On the Self-Regulation of Respiration.—The effect of the 
stimulation of the central end of the vagus on respiration has been 
studied long and carefully, and with varying results, Meltzer finds * that 
weak and — Mie cumenti have — effects in different indi- 
bition of Sesion, followed s soon by an inspiratory after-effect. There 
must then be fibres in the vagus that produce inhibition of inspiration, 
In some individuals medium and weak stimuli produce inspiratory 
effects ; hence there must also be, in such individuals at least, fibres in 
the vagus that bring about inspiration. These may be likened to the 
accelerators of the heart, while the others act like the inhibitors of 
that organ. We may then conceive of the vagus as consisting of two 
kinds of fibres, one producing inspiration, the other inhibiting it. 
When the cardiac inhibitors and accelerators are stimulated together, 
the effect of the former alone is observed during stimulation ; but after 
the latter has ceased the short after-effect of the inhibitor fibres is fol- 
lowed by the larger after-effect of the accelerator fibres, In like man- 
ner, as regards respiration, we may say that the nerve fibres that inhibit 
inspiration have but a brief after-effect, while those that cause it have 
a more prolonged influence. It has been shown that expansion by the 
lungs has the same effect on respiration as a strong stimulation of the 
vagus, producing first inhibitory and then inspiratory after-effects. 
Hering and Breuer formulated a now well-known theory of the self- 
regulation of respiration, the main principles of which are that expansion 
of the lung produces an inhibition of inspiration, while collapse pro- 
duces a following inspiration. Meltzer claims that the latter part of 
this theory is not supported by facts, sii substitutes a new theory 
based on the above conclusions, viz., the existence in the vagus of two 
kinds of fibres, namely, inspiratory and inspiration-inhibiting. —** In- 
spiration expands the lung, thereby stimulating both the inspiratory 
and the inspiration-inhibiting nerve fibres. But during stimulation, and 
for a very short time after cessation of the expansion, the inhibiting 
t N. Y. Medical Journal, Jan., 1890. 
