174 Report on the Pathological Anatomy of Pleuro-pneumonia. 
when the disease is localised to the anterior lobes, which are 
completely walled off from physical examination by the dense 
mass of solid parts forming the shoulder of the beast. 
The number of lobes and their complete separation one from 
the other by means of deep fissures may tend to keep the disease 
isolated, but otherwise the descriptive anatomy teaches us little. 
In the larger air-passages the mode of subdivision is irregular, 
being seldom fork-like, as in the human lung. The trachea 
itself does not bifurcate until it has given off a large separate 
branch to the right anterior lobe. The lobar bronchi give off 
small lateral branches, as they run down sometimes beneath the 
pleura of the long slender lobes, and do not divide dichoto- 
mously. The mode of branching, however, is found to differ 
materially in different lobes, and appears to depend on their 
size and shape, those of the large posterior lobe dividing more 
like the air-passages of the human lung. 
The blood-vessels follow the course and mode of branching 
of the air tubes ; the artery and the vein lying on either side 
of their corresponding bronchus. In the healthy lung the 
vessels and bronchi are surrounded by a quantity of very 
delicate connective tissue, which forms around them a loose 
sheath common to the three, so as to separate them from the 
lung parenchyma. Any, or all, of the vessels may be pulled out 
of this yielding case of soft cobweb-like tissue ; and the delicate 
structures may be torn from their proper coats, with which they 
are thus seen to be directly continuous. The bronchus, artery, 
and vein contained in this sheath may be conveniently referred 
to under the name broncho-vascular system, while the region of 
lung-tissue supplied by any such system may be called bronclio- 
vascular territory (Fig. 1). 
If a thin injection-mass be thrown, with gentle and steady 
pressure, into the interstices of this peribronchial tissue, it 
gradually runs along the outer surface of the bronchus and 
vessels, and permeates into all parts of the connective tissue 
sheath. Thus may be demonstrated the existence of a close 
network made up of an immense number of delicate, irregularly 
sinuous, or lacunar lymph-channels, which completely encom- 
pass the artery and vein, and form around them a sheath of 
lymphatic anastomoses. 
In the very small bronchial tubes which belong to the single 
lobules the mode of branching changes and becomes dichotomous, 
and the branches lie at right angles to each other. Within the 
lobules, the tubes and vessels have no longer the same sheath 
of connective tissues, and I have failed to satisfy myself of the 
existence of any lymphatic vessels around the bronchus in this 
situation. If such exist, they must play a very insignificant 
