224 
Avgas persims 
The Salivary Glands. 
Plates XIV, XV and XVI.yZ.saZ.; Plate XVII, figs. .5 and 6. Text-fig. 1. 
These organs consist of a single pair of large, elongate, cream-coloured, 
glandular masses which occupy a ventro-lateral position in the anterior 
half of the body-cavity. They are situated immediately above the coxae 
of the first three pairs of legs and are almost entirely covered above by 
the anterior coecal lobes of the stomach, with which they are in contact. 
In the active state, they may extend, backwards and outwards, so as to 
reach almost to the spiracles, but it must be noted that their size 
depends to a great extent upon the condition of the tick. In the resting 
phase after engorgement, they may assume quite insignificant pro¬ 
portions, though they rarely show the extreme degree of degeneration 
which is exhibited by the Ixodidae. 
Each gland consists of grape-like clusters of alveoli, loosely aggregated 
into irregular lobules, which surround the main salivary duct {d. sal.). 
This main duct, which commences near the posterior limit of the gland, 
receives numerous secondary ducts which enter it in a very oblique 
manner, one from each of the lobular masses. The alveoli are closely 
clustered on these secondary lobular ducts, each opening by a separate 
short efferent duct which usually entei’s the lobular duct directly, but 
occasionally may unite with the efferent ducts from one or two other 
alveoli, to enter the lobular duct collectively. 
Between the alveoli a sparse connective tissue frame-work is 
developed, which is not sufficient, however, to give more than a small 
degree of coherence to the gland. 
A careful examination of the gland leads to the recognition of two 
types of alveoli. These may be distinguished in the fresh gland, while 
still in situ, under the dissecting microscope, but after treatment wdth 
a fixing reagent such as dilute acetic acid, the two types become strik¬ 
ingly apparent. The first type forms the greater mass of the gland ; 
the second type is limited to a mass of alveoli which are situated in the 
anterior half of the gland on the mesial side of the main salivary duct, 
a little towards the dorsal surface (see Text-fig. 1 B). In longitudinal 
sections of the entire gland, both types of alveoli are readily defined, but 
in transverse sections passing through the posterior half of the gland 
only, alveoli of the first type appear alone. 
Apart from differences in size and the fact that the main ducts are 
generally somewhat flattened in section, the salivary ducts show a com¬ 
plete uniformity, in the principle of their structure, throughout the 
