After respiration they fill the thorax more or less completely, the amount of distension depending, of course, upon the completeness of the respiratory acts on the part of the child. (_b_) _Consistence._--Before respiration has taken place, the lungs feel firm, compact, and resistant, and are of the consistency of liver. After respiration they are spongy, crepitant, and yielding when pressed between the fingers. They also present a marbled appearance. These signs of respiration are more or less modified by disease, and the _atelectasis pulmonum_ of Jörg, jun. Casper denies the existence of _atelectasis pulmonum_ as a distinct disease of newly-born children, and considers that “it is nothing else than the original fœtal condition, from which it differs in no anatomical respect”--an opinion supported by Meigs, who says “it, in fact, resembles exactly the fœtal lung.” It is simply the result of the child dying from some cause before respiration has had time to become fully established, and has possibly been confounded with hepatisation. It must also be remembered that cases are on record of infants having lived for some hours, and then died, yet the lungs sank as a whole, and when cut in pieces. (_c_) _Colour._--The colour of the fœtal lungs is “exceedingly various,” and it is by no means easy to convey the idea of colour by words. Speaking in general terms, the lungs of children who have _not_ breathed are of a reddish-brown liver colour, this colour changing to a brighter red at their margins. In children who _have_ breathed, the lungs are of a slaty-blue colour, more or less mottled with circumscribed red patches. This circumscribed mottling is _never_ found in perfectly fœtal lungs. When the lungs are inflated artificially, they swell up and present a uniform cinnabar-red colour, destitute of insular marbling. The insular marbling of the lungs is characteristic of lungs that have breathed, and is due to the presence of blood in the arteries and veins surrounding the inflated lung tissue. (_d_) _Buoyancy in Water._--Lungs which have respired float in water. But the objection may be raised that lungs that have _not_ respired may yet float from-- 1. The result of artificial respiration. 2. The result of putrefaction. The value of these objections will be discussed in the following pages. The following table is given by Tidy: