270 



NATURE 



[August 25, 1923 



season. Tlic Home Secretary or the Secretary for 

 Scotland, as the case may be, is to l)c given power to 

 transfer birds from one category to another or to change 

 the dates of the close season. He may do this by 

 general order or, with the consent of the local authorities, 

 by local order affecting only a particular district ; and 

 with the consent of the owner and occupier of the land 

 he may make a special order in support of an endeavour 

 to create a bird sanctuary, even to the extent of giving 

 all birds in the sanctuary the full protection of Cate- 

 gory I. In exercising these functions the Secretary of 

 State is to be assisted by an advisory committee. 



The Bill also contains a number of special provisions, 

 some of which are new and others of which are retained 

 from existing enactments. The use of certain types of 

 trap is to be prohibited altogether ; the use of mechani- 

 cally propelled boats or of aircraft is to be prohibited 

 as an aid to killing or capturing birds ; the capture of 

 birds on highways, commons, and public places is to be 

 prohibited ; the killing or capture of birds on Sunday is 

 to be prohibited ; and the catching of birds alive is 

 to be prohibited except under licence granted by the 

 competent local authority. Lastly, the liberation of 

 imported birds is to be permissible only with the 

 authority of the Secretary of State, a wise provision 

 aimed at the prevention of interference with the 

 balance of nature. 



The great advance in legislation of this kind which is 

 marked by this Bill, however, lies in its application 

 not only to offenders caught red-handed but also to all 

 persons found in possession of birds, parts of birds, 

 nests, or eggs which may be presumed to have been 

 illegally taken. The onus of proof is to be thrown 

 wholly on the possessor in the case of birds, nests, or 

 eggs in Category I. and nests or eggs in Category II., 

 and also in other cases during the whole of the close 

 season except its first fortnight. Further, every taxi- 

 dermist and dealer is to be compelled to keep a register 

 giving all particulars of specimens passing through his 

 hands which come under Categories I. and II. If this 

 measure becomes law we may therefore hope to see 

 an end of the scandal that the skins and eggs of some 

 of our rarest and most strictly protected birds may 

 be seen openly displayed in the taxidermists' windows 

 or publicly advertised in the catalogues of dealers. 

 Similarly, it will become an offence to sell or possess 

 " plovers' eggs " after April 20 (allowing five days' 

 grace from the beginning of the close season specially 

 determined as regards the taking of these eggs). 



The Secretary of State is to be empowered to grant 

 special licences to kill or take protected birds or to take 

 their eggs or nests either for scientific purposes, for the 

 protection of crops, property or fisheries, or for other 

 special reasons. The potential exemption from the 



NO. 2808, VOL. 112] 



law in favour of scientific purposes is a useful n< 

 provision, but it is to be hoped that the power will l>e 

 very sparingly exercised in view of the great amount of 

 useless collecting, especially of eggs, which masquerade > 

 under the name of science. 



The Capillary Blood-Vessels. 



The Anatomy and Physiology oj Capillaries. By Prof. 

 August Krogh. (Silliman Memorial Lectures.) 

 Pp. xvii + 276. (New Haven: Yale University 

 Press ; London : Oxford University Press, 1922.) 

 135. 6d. net. 



EVERY cell of the body is brought into material 

 relationship with all other cells in virtue of 

 the existence of a common medium, the blood, which 

 is maintained in constant circulation throughout the 

 body. Substances absorbed into the blood from the 

 exterior, either through the external or internal sur- 

 faces of the body, are thus brought round and pre- 

 sented to every cell, to be taken up or rejected accord- 

 ing to the needs of the latter. In the same way the 

 products of the chemical changes occurring in any 

 cell are distributed to all other cells, so that the blood 

 represents the internal environment integrating the 

 metabolic activities of all parts of the body. The 

 interchange between blood and tissues takes place 

 only in the capillaries and smaller veins, so that we 

 may say that the whole vascular system — heart, 

 arteries, and veins — exists to ensure an adequate 

 passage of blood through the capillaries. It is there- 

 fore rather surprising that the physiology of the 

 capillaries has been comparative!}^ neglected until 

 the last few years. There have been isolated observa- 

 tions with regard to their structure and contractility 

 and the properties of their walls. Some twenty-five 

 years ago, when the question of lymph production 

 and absorption was brought into prominence by the 

 researches of Heidenhain, the functions of the cells 

 forming the capillary walls were hotly debated, but 

 after a few years, interest in the matter died down, 

 and physiologists failed to appreciate or to follow 

 up the many other problems concerning the capillaries 

 which were implicit in the problems of lymph pro- 

 duction. 



By a study of injected specimens, or of the circula- 

 tion in the lung or web of the frog, it can be seen 

 that an arteriole breaks up into a large number of 

 capillaries, each of which may have a diameter approxi- 

 mating to that of the arteriole. The relations in this 

 part of the circulation have thus often been compared 

 to those in a narrow stream flowing into a lake, and 

 it has been tacitly assumed that the circulation through 

 the capillary network as well as the state of dilatation 



