34 
obtained. If this be placed on a slide which has been slightly 
wetted with a decinormal solution of NaCl, and the super- 
fluous fluid taken up by filter paper, on examining the in- 
testine under the miscroscope peristaltic waves of con- 
traction are seen travelling down the intestine towards the 
rectum at an easily followed, uniform velocity, with moderate 
frequency. On now touching the intestine at about its middle 
point with a fine pointed camel's hair brush, which has been 
just wetted with a decinormal solution of CaCl^, a remark- 
able effect is observed : — If one of the peristaltic waves start- 
ing at the end of the intestine furthest from the rectum be 
followed with the eye, it is observed to completely disappear 
on entering the region which has been treated with CaCL, ; 
but if we continue to move the eye along the intestine at the 
same rate as the wave of contraction was formerly moving, on 
reaching the other end of the affected area the wave will be 
seen to emerge from it as vigorous as before, and to be travel- 
ling at the same rate. Thus, contraction has been abolished 
by the CaClg, while conduction continues to take place at 
the same rate as before. The suppression of the wave of con- 
traction in the area affected is not due to any apparent 
change in form in the intestine in that area, for if the CaClj 
be properly applied, no apparent change in form takes place. 
If, however, too much CaCla is applied^ — ^so that it is not 
sufficiently diluted by the NaCl present (e.g., a small drop) — 
the intestine at that part is thrown into corrugations which 
represent fixed contractions ; that is, the intestine at that part 
acquires ''tone" (the cause of this will be considered later), but 
this does not alter the effect of the CaCl> upon incoming 
waves of contraction, which enter, and are suppressed, and 
re-appear at the other end of the affected region as before. 
Care must be taken in these experiments not to have the in- 
testine too wet, otherwise it is difficult to confine the effect 
of the CaCl^ to a given region, as the CaCl, is carried 
about by currents in the water. I repeated this experiment a 
number of times, and, when the above-mentioned precautions 
had been taken I never failed to get the effect described. I 
also obtained the same effect using a decinormal solution of 
BaCl.2 instead of CaClj. On glancing at the table of stimulation 
efficiencies in section 4, it will be seen that both CaClg and 
BaClg have high negative stimulation efficiencies, so 
that our theoretical deduction is confirmed by these experi- 
ments. The action of CaCla and BaClg, when applied to 
a limited region of the intestine, may be contrasted with that 
of a decinormal solution of KCl when similarly applied, al- 
though no more apparent change of form is produced in the 
intestine by the KCl than by CaClg; yet not only is the 
