Anatomy and physiology

This chapter covers some fundamental aspects of the respiratory tract, and describes the structure and function of both the upper and lower airways, processes by which air is moved from the external environment to the gas exchange area of the lungs, and some of the aspects of the normal respiratory tract which are affected by the more common respiratory diseases. Its functions in terms of respiration are to facilitate the uptake of oxygen; eliminate carbon dioxide; and maintain the pH of the blood. Conventionally the tract is divided into upper and lower parts. The upper tract is composed of the mouth, nasal passages, and behind these a wide tube termed the pharynx. This receives inhaled air from the nose and mouth and accordingly is termed the naso- and oropharynx, respectively.

Linaria argillicola (Plantaginaceae), a new species of L. sect. Supinae from the southern Iberian Peninsula

A new species of the genus Linaria is described, illustrated and compared with its morphologically closest relatives from L. sect. Supinae: L. accitensis, L. aeruginea, L. tristis and L. badalii. A principal component analysis (PCA), correspondence analysis (CA), and linear discriminant analysis (LDA) were carried out for morphological differentiation. The species is characterized by long abaxial sepals, corolla mostly yellow or rarely reddish with wide tube, wide winged seeds with a tuberculate seminal disc, and a non-continuous fruiting inflorescence. Linaria argillicola is an edapho-endemic species, growing on the marly gypsiferous deposits from the Guadiana Menor river basin, on the border of Granada and Jaén provinces (Andalusia, Spain).

The Site of Formation of Hypotonic Urine in the Nephridium of Lumbricus

1. Methods for the collection of samples of urine from different parts of the nephridium of Lumbricus are described. 2. The osmotic pressures of these samples have been measured by determination of freezing-point depression and have been compared with the osmotic pressure of the medium surrounding the nephridium. 3. The results of this comparison indicate that the ability to form hypotonic urine is certainly present in the wide tube, is possibly present in the middle tube and is probably not present in the narrow tube. 4. The analogy between the nephridium and the vertebrate nephron is discussed.

The Long Spacing in Rubber

The x-ray diagrams of some rubbers give a long spacing, which was first reported by Clark and collaborators. According to them, it is found only in gel rubber, where it has the value of 54 a.u., but it is absent in sol rubber. This spacing is oriented in stretched rubber, the x-ray reflections contracting into two spots in the equatorial plane. This means that the long spacings lie in planes at right angles to the fibre axis. As we found it difficult to account for this result and, furthermore, had indications that this long spacing might depend on the nature of the rubber, we examined a number of specimens of different origin and preparation. We used a camera of about 10-inch radius, reducing the air scattering by inserting an evacuated length of wide tube with thin cellophane windows at both ends. The x-ray source in these experiments was the 50 kw. x-ray generator of this laboratory, working with an input of 30 to 40 kw.

On the theory of the capillary tube

A recent paper by Richards and Coombs discusses in some detail the determination of surface tension by the rise of the liquid in capillary tubes, and reflects mildly upon the inadequate assistance afforded by mathematics. It is true that no complete analytical solution of the problem can be obtained, even when the tube is accurately cylindrical. We may have recourse to graphical constructions, or to numerical calculations by the method of Runge, who took an example from this very problem. But for experimental purposes all that is really needed is a sufficiently approximate treatment of the two extreme cases of a narrow and of a wide tube. The former question was successfully attacked by Poisson, whose final formula [(18) below] would meet all ordinary requirements. Unfortunately doubts have been thrown upon the correctness of Poisson's results, especially by Mathieu, who rejects them altogether in the only case of much importance, i. e. when the liquid wets the walls of the tube-a matter which will be further considered later on. Mathieu also reproaches Poisson's investigation as implying two different values of h , of which the second is really only an improvement upon the first, arising from a further approximation. It must be admitted, however, that the problem is a delicate one, and that Poisson's explanation at a critical point leaves something to be desired. In the investigation which follows I hope to have succeeded in carrying the approximation a stage beyond that reached by Poisson. In the theory of narrow tubes the lower level from which the height of the meniscus is reckoned is the free plane level. In experiment the lower level is usually that of the liquid in a wide tube connected below with the narrow one, and the question arises how wide this tube needs to be in order that the inner part of the meniscus may be nearly enough plane.