218 General Notes. (February, 
Martin and his pupils (Stud. Biol. Lab. J. H. Univ. Vol. 1, No.2, 
Trans. Med. Chirurg. Fact. Md. 1882). It has been found that 
variations of enormous extent of either arterial pressure, the re 
sistance to the outflow of blood from the heart, or of venous 
pressure, that under which blood enters the heart, have no effect 
whatever upon the pulse rate. The work has furthermore sug 
gested to its author some simple explanations of the causes of the 
conflicting results of previous experimenters. But Martin has 
found, as was to be expected, that, though the pulse rate is unaltered 
by great changes in the mechanical conditions under which the 
heart acts, the organ. is extremely susceptible to changes of tet- 
perature, and beats uniformly quicker or slower as the temperature 
of the blood entering it rises or falls the fraction of a degree. The 
application of this new method of studying the mammalian heart 
opens the way for a series of researches that promises rich results ; 
for physiology. T 
In connection with this subject, the recent work of Ludwig and 
Luchsinger is of considerable interest (Pfliger’s Archiv. Bd. XXV). 
These authors showed.that the inhibitory power which the pneu- 
mogastric nerve when stimulated, exercises over the heart-beat of 
the frog, is diminished or altogether overcome by increasing intras 
cardiac pressure. Later, Sewall and Donaldson taking up the : 
same line of work (loc cit.), have found that it is only the Mt 
pressure within the venous chambers of the heart which has at 
effect in modifying the power of pneumogastric inhibition; thus 
showing that changes in the hydrostatic conditions under whieh 
the heart works may affect the action of that organ „indirect 
“1. 3 
A o] RY 
. 
while the muscular servant, the heart, has enough to do 10° 
on its work of prime importance, and is blind and deaf to? 
all occurrences except those messages that reach it from: 
quarters. i ae 
