494 
JACOB HELMER. 
detect physical signs. Inspection of the exterior of the chest 
reveals its form or shape, and the number and character of 
its movements. We need not dwell upon the idea of Form. 
It generally indicates in the horse degrees of vital capacity 
consistent with excellent health. Tubercular tendency or 
disease in the human family renders study of the form and 
size of the chest practical and necessary. 
The movements of the chest are of great importance since 
they constitute the first steps of the act of respiration, and all 
other steps depend on them. A respiratory act consists of 
an inspiration and expiration and a pause. This cycle is 
completed by a contraction and expansion of the chest walls. 
In health and at rest the movements of contraction and 
expansion are normal in number and character. When above 
normal number they are frequent, as during exercise. Fre¬ 
quency of movement not caused by exercise or thermic con¬ 
ditions is a sign of disease. Infrequent respiratory move¬ 
ments are abnormal and are usually due to morbid changes 
in the brain or the action of narcotic poisons. 
The movements of the chest walls may be partial or com- 
plete. A partial or limited movement of contraction signifies 
shallow respiration and the use of little air in the lungs. A 
complete or extended contraction indicates powerful and 
deep respirations and the change of much air in the lungs. 
These characters may be both frequent and infrequent. 
The natural rhythm of the movements may be disturbed ; 
hence these may alternately be regular and irregular. Again, 
the relation existing between the thoracic and abdominal 
movements in health may be broken. When by conditions 
of disease constriction of the thoracic muscles and diaphragm 
occurs, thus lessening their normal movement and amount of 
work, these movements in the assisting abdominal muscles 
become increased. This is well marked in pleurisy, where 
the abdominal muscles are brought to perform an unusual 
amount of work, while the thoracic muscles are more or less 
fixed on account of pain in the inflamed pleura. In peritoni¬ 
tis, where the pain is felt under the region of the abdominal 
muscles, these become fixed and the normal movements of 
