224 Prof. J. C. Schjédte on Phthiriasis, and 
At the top of the head, under the transparent skin, between 
and a little in advance of the eyes, a triangular blood-red point 
appears, which is in continual movement, expansion and con- 
traction alternating with increasing rapidity. Soon this pulsa- 
tion becomes so rapid that several contractions may be counted 
ina second. However, we must turn our attention elsewhere ; 
for the whole digestive tube is now in the most lively peristaltic 
movement, filling itself rapidly with blood, as is easily observed ; 
the long cesophagus is particularly agitated, throwing itself from 
one side to another inside the neck, bending itself so violently 
as to remind one of the coiling of a rope when being shipped 
on deck. We seize our most delicate scissors, and, without 
touching any other part of the animal or displacing the head in 
the least, the latter is divided by a transverse eut just in front 
of the eyes. The fore part of the head is still firmly attached to 
the skin, but is now slowly and cautiously taken away with the 
forceps and placed under the microscope. And now * we per- 
ceive a short, dark-brown, protruding haustellum, provided with 
hooks at its extremity, out of which an excessively delicate 
membranaceous tube, of varying length, is hanging. We natu- 
rally wish to use a higher magnifying-power, and cover the 
preparation with a thin glass; but in a moment all the 
protruding parts disappear, and we have the old image with 
“mandibles” and “palpi.” Repeated attempts prove equally 
fruitless ; the slightest pressure chases everything back into the 
head again. But we are evidently on the right scent. We choose 
for dissection the largest, for examination with the microscope 
by transmitted light the smallest and lightest specimens, whose 
skin is most transparent; we alternate with fresh specimens 
such as have been for some time preserved in spirit of wine, 
and at last we arrive at some certain knowledge of the whole 
mechanism. 
The muscles inside the head appear to belong to four divisions. 
That those of the neck are very strong cannot surprise us, as we 
witnessed how the animal bent its head downwards so as to 
form an angle with the thorax, and kept it in that position 
during the whole act of suction; but neither these muscles nor 
those belonging to the antennz concern us here. So much the 
greater attention must we bestow on the two other groups of 
muscles, viz. a large conical bundle filling up the greater part of 
that section of the head which is in front of the insertion of the 
* Swammerdam warns us, at the beginning of his description of the 
mouth, against foregone conclusions: ‘ But this proboscis is, on account 
of its diminutive size, not to be demonstrated except with great pains- 
taking, and it is perhaps nothing but a piece of good luck if one succeeds 
in seeing it.” (Bibl. Nat. i. p. 74.) 
