THE ANATOMY OF GUSTATION 127 



bladder by tlie ])uounuitic bulb. The taste-buds, it Avould appear, 

 act as sentinels and discriminate between the food and the swallowed 

 froth, which can be observed lying at the orifice of the pneumatic 

 duct. "When it is borne in mind that in man taste-buds are known 

 to be present not only on the tongue but also on the anterior pillars 

 of the fauces, the under surface of the palate, the pharynx, and the 

 epiglottis, it becomes clear that in man also these organs must at 

 times have a function other than true taste and can also be regarded 

 as sentinels, particularly those situated on the epiglottis, which is an 

 important part of the mechanism which prevents food " going the 

 wrong way." 



The barbels of fish are usually well supplied with taste-buds 

 and they have been described on the margin of the anterior nostril ; 

 but perhaps the most unusual position in which they have been 

 found is in the site of the dorsal fin in the rockling. 



It is clear from the facts above, given as to the site of taste-buds, 

 that these organs can perform different functions, and we can give, 

 as an example, the exercise of these functions as they occur in a 

 carp. In the process of feeding the fish first of all recognise the 

 presence of food by smell, which may be called a distance receptor ; 

 the food is then examined by the gustatory organs, the taste-buds 

 on the lips and barbels, and, if considered satisfactory, it is passed 

 on to the palatal organ which, in mud feeding fish, separates the 

 inorganic particles from the proteins and carbohydrates present in 

 the mud before passing the nutrient material into the gullet ; the 

 imiervation of the first stage of taste is by the facial nerve, and the 

 central connection in the brain is the facial lobe ; the innervation 

 of the second stage is by the vagal nerve and the central connection 

 is the vagal lobes. Again, when the carp swallows air, the air must 

 pass the taste-buds in the lips and after being swallowed passes with 

 a certain amount of mucus into the gullet and thus reaches the 

 orifice of the pneumatic duct where it is recognised by the taste-buds 

 there present ; the pneumatic bulb then sucks in the air bubbles and 

 drives the gas into the swim-bladder. The innervation of these 

 taste-buds is also by means of the vagal nerve and the central 

 connection is the vagal lobes. 



It would appear, therefore, that the facial lobe is concerned with 

 purely gustatory sensations, whereas, the vagal lobes have a dis- 

 criminatory function allied to taste which enables the animal to 

 sort and sift, retain or reject, by means of the palatal organ and 

 also to separate air bubbles from solid matter by means of the 

 sentinel ring of taste-buds guarding the orifice of the pneumatic 

 duct. These considerations have also their counterpart in the 



