244 ANATOMY. 



even observe at the base a much greater thickness of the wing, which 

 is caused by the two layers of the epidermis not having closely joined 

 together. Upon the margin of the wing the two layers pass into each 

 other, and thus the bag is formed. This bag admits of being distinctly 

 represented as such, if just-developed insects be placed in spirits of 

 wine; the fluid then passes between the still fresh and soft membranes 

 of the wing, and filling their internal space, distends them like a bag. 

 Heusinger* observed this in fresh specimens of butterflies, and I have 

 myself detected it in a young individual of Anthophagus plagiatus, 

 Grav. 



Howsoever smooth, fine, and transparent the membrane of the 

 wing appears to the naked eye, an investigation with the microscope 

 reverses this, and exhibits it as covered with innumerable small hairs, 

 which rise from bulbous roots upon the wing, and densely cover its 

 whole surface. In some insects, for example, the common gnat, they 

 are longer, broader, and lanceolate, and pass over into the scales of 

 butterflies, which are absolutely nothing else than transformations of 

 the hair peculiar to almost all insects. 



The ribs of the wings are hollow, horny tubes, by which the two 

 plates of the wings are supported. Their situation and reciprocal 

 relation, as well as the cells formed by their connection, we have 

 become acquainted with above : we will merely add here, that each 

 rib is filled internally with a soft parenchyma, in which I have 

 detected a vessel very large in compass, and by the side of it a fine 

 nerve. The vessel appeared to come from the cavity of the thorax, 

 and the nerve entered from the same part, coming probably direct 

 from the approximate ganglion ; therefore, close to the posterior wings 

 in beetles, upon which I made the observation, and from the third 

 ganglion of the thorax. In the vessel itself I could detect no structure, 

 and, least of all, the spiral fibre observable in the tracheae, even upon 

 an enlargement of three hundred tiniest. I thence conclude that it is 

 a blood-vessel, which is supported by Cams' observation of the motion 

 of a fluid in the ribs of Lampyris. How else could the wings be 

 distended, were not the liquid flowing into these vessels the cause of 

 it ? But it is not necessary that we should thence conclude upon a 



* System der Hystologie, 2 Heft. 



t I have since detected the spiral fibre in these vessels, and observed that they are 

 genuine tracheae Authors MS. Note. 



