The trilobation of the head and body - due to the expansion and flattening of the sides or "pleura" of the tegumentary skeleton - is so closely repeated in the young of Limulus that the latter has been called " the trilobite stage " of Limulus (fig.
38), like that of Limulus and Scorpio, and that lateral spines on the pleura of the somites are frequent as in Limulus, and that neither metasomatic fusion of somites nor post-anal spine, nor lateral pleural spines are found in any Crustacean, nor all three together in any Arthropod besides the trilobites and Limulus - the claim of the trilobites to be considered as representing one order of a lower grade of Arachnida, comparable to the grade Entomostraca of the Crustacea, seems to be established.
As regards pulmonary disease, pneumonia has passed more and more definitely into the category of the infections: the modes of invasion of the lungs and pleura by tuberculosis has been more and more accurately followed; and the treatment of these diseases, in the spheres both of prevention and of cure, has undergone a radical change.
In the treatment of effusions into the pleura and, though with less advantage, of pericardial effusions, direct mechanical interference was practised by one physician and another, till these means of attaining rapid and complete cure took their places as indispensable, and were extended from thoracic diseases to those of the abdominal and other inner parts formerly beyond the reach of direct therapeutics.
In the thorax the pronotum and prosternum are closely associated with the mesothorax, but the pleura of the prothorax are usually shifted far forwards, so that the forelegs are inserted just behind the head.
Of the abdominal pleura) which when pressed together form a tube whose point can pierce the surface film and convey air to the hindmost spiracles which are alone functional in the adult.
6) or water-scorpions (q.v.) - two British species - are distinguished by their threesegmented feelers, their raptorial fore-legs (in which the shin and foot, fused together, work like a sharp knife-blade on the grooved thigh), and their elongate tail-processes formed of the abdominal pleura and used for respiration.
This head-shield is succeeded by a varying number of free segments, each of which consists of a medium convex tergal piece and a pair of arched lateral plates, the pleura, of which there is one on each side.
The terga and pleura of each individual segment overlap those of the segment that serially succeeds it.
The right surface of the liver is covered with peritoneum and is in contact with the diaphragm, outside which are the pleura and lower ribs.