496 
JACOB HELMER. 
respiratory movements. A second series of measurements 
are made, beginning at a given point on the withers to the 
commencement of the cartilage of the false ribs, beginning 
with the eighth. Again from the lower end of the third rib 
to the same points. Lastly, along the middle of the chest, 
from the posterior border of the shoulder to the margin of 
the last rib. These measurements are made at the same 
points on both sides of the chest, and at the same point of 
contraction and expansion of the chest walls. 
Of the methods of physical examination applied to detect 
diseases of the chest, the most important ones to us are aus¬ 
cultation and percussion. Before applying these methods let 
us, for convenience and accuracy, divide the chest into three 
regions; an anterior and two lateral. The lateral regions 
may be further sub-divided in nearly three equal parts by 
drawing two horizontal lines across the chest. These sub¬ 
divisions are a superior, a middle and an inferior third. The 
superior third contains lung substance, closely in contact 
with the internal wall. The middle third contains much lung 
substance ; also the large bronchial tubes in its anterior part, 
and the large blood vessels at the base of the heart. In the 
lower third there is less lung substance, but in its anterior 
part the heart is principally situated opposite the third, 
fourth, fifth and sixth ribs. This area, sometimes designated 
the triangular space, is covered by the forearm and its exten¬ 
sor muscles. The limb must be pulled forward in order to 
examine the region over the heart. 
Auscultation is the art of listening over a part to detect 
abnormal sounds and especially the condition that gives rise 
to them. It is the most important method of physical diag¬ 
nosis. It was discovered by Reno Theophile H. Laennec, 
who lived from 1781 to 1826. It was introduced into veter¬ 
inary practice by Delafond and Leblanc. The facts elicited 
by auscultation and percussion and their verification by post 
mortem examination revolutionized the knowledge then in 
existence of the disease of the chest and began an area of ex¬ 
act demonstration. 
Auscultation is of two kinds, mediate and immediate. In' 
