536 MENSURATION. 



middle of the sternum, which part is marked by a knot ; a 

 second measurement is made from the withers to the lower end 

 of the 8th rib, or the commencement of the cartilages of the 

 false ribs, and similarly marked; a third measurement is made 

 from the lower end of the 3rd rib to the commencement of 

 the cartilages of the false ribs; lastly, the tape may be car- 

 ried from the posterior border of the shoulder along the 

 middle region of the chest, as far as the last rib. The 

 same measurements may then be made on the opposite side 

 of the thorax, care being taken that they be always made 

 at the same stage of the respiratory act, as otherwise false 

 results will be obtained. It is well, indeed, to measure the 

 different parts after both inspiration and expiration, that any 

 difference in the expansion of the two sides of the thorax 

 may be ascertained. In some of the smaller animals, as the 

 dog and sheep, the variations in the expansion of the two 

 sides of the thorax may be noticed by inspection only ; in 

 this case, the practitioner stands at a short distance behind 

 the animals, and examines the relative movements of the two 

 sides during the respiratory process. 



The greater dilatation of one side is noticed in cases of 

 hydrothorax in the dog and cow, especially when confined to 

 one side, and of some standing. In such a case, the inter- 

 costal spaces may be observed to be larger than usual. 

 Delafond notices a similar increased dilatation as a result 

 of a nearly complete hepatisation of one lung. 



A decrease of the volume of the thoracic parietes is 

 commonly an accompaniment of chronic disease of the lung, 

 with atrophy of pulmonary substance. 



SUCCESSION. 



Succussion consists in grasping the thorax between both 

 hands, and shaking it quickly, so as to elicit sound. It is 



