CAPILLARIES. 



[ 109 ] 



CAPNODIUM. 



stance contained in the milky juices of many 

 plants, but most abundantly in those of the 

 families Euphorbiacese, Urticacese and Apo- 

 cynaceae, whence the India-rubber of com- 

 merce is obtained. The caoutchouc appears 

 in the form of minute globules suspended in 

 a watery fluid containing a gummy substance, 

 so that the milky juices may be regarded as 

 a kind of emulsion. For further details, see 



CAPILLARIES. — The minute vessels 

 which the blood traverses in passing from 

 the arteries to the veins. 



The capillaries consist of a delicate, trans- 

 parent, tolerably resisting and elastic struc- 

 tureless membrane, and a number of oval or 

 rounded longitudinal nuclei. The diame- 



Fig. 103. 



Magnified 300 diameters. 



One of the smallest vessels from the arterial side. 1, 

 smallest artery ; 2, transition vessel ; 3, large capillaries ; 

 4, small capillary, a, structureless membrane with few 

 nuclei, representing the adventitious coat ; b, nuclei of 

 the muscular fibre-cells ; c, nucleus inside the small 

 artery ; d, nuclei of the capillaries and intermediate 

 vessel. From the human brain. 



ter of the human capillaries varies from 

 1-5000 to 1-1000", the most common being 

 perhaps 1-3000". The size of the capillaries 

 in the Vertebrata generally, bears a relation 



to the size of the coloured corpuscles of the 

 blood. Thus, they are largest in Birds, 

 Fishes and Reptiles. The larger capillaries 

 have thicker walls and more numerous nuclei 

 than the smaller ones; and in the former, 

 the nuclei are situated in the substance of 

 the wall or membrane, whilst in the latter 

 they appear to be attached to its inner 

 sm'face. 



The capillaries branch and anastomose 

 freely, giving rise to the beautiful networks, 

 so well known as favourite microscopic 

 objects when injected. 



The most important pathological change 

 which the capillaries undergo is that of 

 Fatty Degeneration. The general 

 arrangement of the capillaries is best seen in 

 injected preparations (Injection). Their 

 structure may be examined in minute pieces 

 of well-washed brain, or of the retina; a 

 minute portion of washed lung, will answer 

 the purpose well. These should be dissected 

 with the mounted needles. The relation of 

 the capillaries to the sm'roimding minute 

 structures may be shown in portions of tissue 

 which have been imperfectly injected, or 

 injected with a liquid containing a small 

 quantity only of colomdng matter ; in these, 

 the capillaries may be recognized by their 

 containing the scattered granules of the 

 colouring matter. Acetic acid is frequently 

 of use in rendering the tissue transparent, 

 and bringing the nuclei to light. 



See Vessels and Circulation. 



BiBL. Paget, Report, Sfc, Brit, and For. 

 Med. Rev. 1842, xiv.; Kolliker, Mikr. Anat. 

 bd. ii. ; Henle, Allgemein, Anat. ; Wedl, 

 Grundzuge d. path. Hist. 



CAPNODIUM, Montague.— A genus of 

 Antennariei (Physomycetous Fungi) growing 

 as a kind of mildew on leaves and shoots, 

 forming a blackish flocculent coat composed 

 of short, branched, beaded or moniUform 

 filaments, densely interwoven. The peri- 

 thecia arise vertically from this, and are 

 either simple or branched, at first simple 

 sacs, but probably afterwards thickened by a 

 layer of cells; a number of threads ultimately 

 grow up from the mycelium, partially cover 

 the central sac, and, closely crowded, some 

 of their tips project beyond it, forming a 

 fringe; the cells of this fringe readily become 

 detached and appear to reproduce as conidia. 

 The central sac contains largish delicate asci, 

 probably often absorbed at an early period 

 so as to set the spores free in the cavity. 



Most of the species are foreign, but C. 

 {Fumago) quercinum, Pers., grows on oak- 



