Feb. 1 8, i886j 



NA TURE 



563 



complete a class of micro-organisms of the greatest im- 

 portance from the number of pathogenic forms it con- 

 tains. Genus 5 is tlie Vibrio of ordinary putrefaction; 

 screw-form threads in long or short links ; spore-forma- 

 tion present. Genus 6, Clostridium (same as bacillus, 

 but spore-formation takes place in characteristically 

 enlarged rods). In this genus are the bacillus of 

 butyric acid fermentation, which converts the lactic acid 

 of milk into butyric acid, and produces the ripening of 

 cheese, and the Clostridium of symptomatic anthrax, the 

 cause of " black-leg" or " quarter-evil " in cattle. 



Group III., Leploihrichea, contains the following 

 genera : (i) Crenothrix (threads articulated, cells sul- 

 phurless, habitat water), occurring in wells and drain- 

 pipes. (2) Beggiaioa (threads unarticulated, cells with 

 sulphur-granules, habitat water), of which the best-known 

 is Beggiatoa alba, or the " sewage fungus," found in 

 sulphur-springs and marshes, as well as in sewage- 

 polluted streams. (3) Phragmidiothrix (threads joint- 

 less, successive subdivision of cells is continuous, cells 

 sulphurless, habitat water), found attached to crabs in 

 sea-water. (4) Leptothrix (threads articulated or un- 

 articulated, successive subdivision of cells not continuous, 

 cells sulphurless), found in carious teeth. 



Group IV., Cladoihrichea (possessing cocci, rods, 

 threads, and spirals : thread-forms provided with false 

 branchings), contains Cladothrix dichotoma, said to be 

 the commonest of all Bacteria in both still and running 

 water, in which organic substances are present. 



Amongst species of Schizomycetes mentioned by writers, 

 and not described or not recognised as distinct species 

 in the preceding classification, are Micrococcus indicus, 

 Micrococcus scpticus, Micrococcus endocarditicus. The 

 micrococci of measles, scarlatina, cerebro-spinal menin- 

 gitis, typhus, acute yellow atrophy of the liver, whooping- 

 cough, puerperal fever, gangrene, yellow fever, dental 

 caries, and saliva. Most of these organisms are only 

 known to be associated with the diseases in question, the 

 causal relations, if existent, have yet to be determined. 

 In this chapter are also described Bacterium termo of 

 common putrefaction. Bacterium lactis, Bacillus Jigurans, 

 the bacillus of swine fever, the bacillus of choleraic 

 diarrhcea from meat-poisoning, the bacilli of septicaemia 

 in man, of syphilis, and of rhinoscleroma, the comma- 

 bacillus of the mouth, various forms of spirillum and 

 monas, Proteus vulgaris, described as intimately con- 

 nected with the process of putrefaction, Actinomycetes, 

 said to be the cause of actinomycosis, a disease of the 

 jaws and lungs in men and animals, and many others too 

 numerous to mention. 



An appendix is devoted to the consideration of the 

 yeast-fungi, or Sacc/iaromycetes, and of the mould-fungi, 

 or Hyphomycetes ; under the latter are described the 

 various species of Mucor, Oidium, Aspergillus, &c. The 

 volume concludes with an account of Koch's methods for 

 the examination of air, water, and soil, with a view to 

 the detection and recognition of their contained micro- 

 organisms. 



Enough has probably been said to show the wide range 

 covered in this work and the full and able manner in 

 which its matter has been treated. On the importance 

 of the subject and the want that has been supplied by 

 the production of a work that has condensed into one 



volume a subject, the literature of which in English is 

 diffused in numerous reports and periodicals, we have 

 already remarked. The numerous coloured plates of 

 test-tube and potato cultivations and those of microscopic 

 appearances are admirably designed and executed, and 

 greatly enhance the value of the work. 



The book, we believe, will be widely read and appre- 

 ciated by all interested in science. 



THE ANATOMY OF THE NETTLE 

 Recherches anatomiques sur les Organes z'dgetatifs de 



/'Urtica dioica, Z. By A. Gravis. (Brussels, 1885.) 

 A WORK of more than 250 pages devoted exclusively 

 ■^^ to the anatomy of the vegetative organs in one 

 species of nettle is a publication of a somewhat unusual 

 kind, even in these days of scientific specialisation. The 

 author has evidently bestowed a vast amount of labour 

 on his subject. He states in his introduction that no less 

 than 15,000 sections had to be made in the course of his 

 investigation of this one plant, and twenty-three beauti- 

 fully executed plates bear witness to the laborious accu- 

 racy with which the work has been carried out. The 

 treatise is one which hardly admits of an abstract, as in a 

 monograph of this kind details are everything. We shall 

 only attempt to give a sketch of the order in which the 

 author has arranged his facts, and to indicate one or two 

 points on which his conclusions have some general 

 interest. 



The investigation was originally intended to serve as a 

 basis for a general comparative study of the family 

 Urticaceas. The question of the value of anatomical 

 characters in classification is one which has engaged the 

 attention of many botanists during the last few years. 

 So far the results have proved of very unequal importance 

 in different cases. The author notices the much more 

 considerable part played by anatomy in zoological than 

 in botanical classifications. This he attributes in a great 

 degree to the frequent neglect on the part of botanists to 

 examine every part of the plant in question, at all ages, 

 and under varying biological conditions. Too often one 

 or two sections are made, almost at haphazard, from each 

 species, with the result that things not truly comparable 

 are frequently compared. One of the main objects of the 

 work before us is to show how great the variations are 

 which are due to the differences just mentioned. 



The treatise is divided into three parts, devoted respec- 

 tively to the stem, the leaf, and the root. The first part 

 begins with a general account of the external conforma- 

 tion of the stem of the nettle, and its systems of sub- 

 aerial and subterranean branches. For the purposes of 

 his exposition the author divides the stem into segments, 

 each segment including a node, with the lower half of the 

 internode next above it and the upper half of that next 

 below it. He then proceeds to classify the variations of 

 structure investigated. First he distinguishes variations 

 according to level, by which he indicates the difterent 

 structures shown by transverse sections of different parts 

 of the same segment, the most important of these differ- 

 ences being those between the nodal and internodal 

 structure. Next come variations according to age, namely, 

 those which are presented by corresponding sections 

 taken at different periods of development. The third 



