298 MR. YOU ATT S VETERINARY LECTURES. 
these tubes and vessels to their termination in the lobuli of the 
lungs. 
Function of these Branches .—There have been contradictory 
accounts of the consequences of dividing the cerebro-visceral 
nerve, with reference to the function of respiration. In the ge¬ 
nerality of cases, and when the nerve has been divided about the 
middle of the neck, the respiration has almost immediately be¬ 
come quickened and laborious, and the animal has shortly died : 
post-mortem examination has afterwards shewn that the vessels 
of the lungs are gorged with blood, and the bronchial cells clog¬ 
ged up with a serous or mucous effusion. Although, therefore, I 
have stated in a former lecture, that the lungs are passive in the 
double act of respiration, or that their only active power consists 
in the elasticity of their cellular membrane and air-tubes; that 
they yield to the pressure of the diaphragm and the ribs in the 
act of expiration, and, that pressure being removed, the cells and 
the tubes start again, and resume their previous form and caliber, 
yet this must be received with some limitation : there is an inhe¬ 
rent power in the bloodvessels to hasten the circulation of the 
blood through them, and also in the bronchial tubes to expel not 
only the air, but the secretions which they contain. This is de¬ 
rived from the cerebro-visceral nerve, and when the influence of 
that nerve is removed, the vessels remain filled with blood, and 
the bronchial tubes with serum. In these respects the cerebro- 
visceral is certainly a motor nerve. 
Different Results of the Division ofthis Nerve .—There is a very 
considerable difference, however, in the result of these experi¬ 
ments. When extreme difficulty of breathing has been produced 
by the division of the nerve, it has been immediately relieved by 
making an opening into the trachea ; shewing that a great deal 
of the disordered function, and perhaps the death of the animal, 
was produced by the closing of the glottis. The result was also 
different according to the place in which the division was made; if 
high up in the neck, the effect was striking and satisfactory; but 
if close to the formation of the plexus, the disarrangement of the 
function was considerably less, and in some cases, very slight. 
There is not much difficulty in accounting for this, when we con¬ 
sider the frequent anastomoses between the two visceral organic 
nerves, and the share which the great organic nerves take in the 
formation of all those plexuses. If the division is high up, there 
will be few or no anastomoses, and few or no fibrils of the cerebro- 
visceral will reach the plexus through the medium of the great or¬ 
ganic ; if the division is close upon the plexus, the communication 
through the main trunk may be cut oft’, but it may be still kept up 
by means of many anastomosing fibres, through the medium of the 
great organic. In one instance, the animal lived three days after the 
