;24 



NA TURE 



[February 2, 1899 



of Mr. Hutchinson, who has written a powerful 

 letter to the Times. In this letter he sets forth how 

 easy it would be to arrange to use the clinical 

 material at the docks in connection with an institution 

 which is at present appealing to the public for funds, 

 viz. the I'ost-CJraduate Medical Polyclinic in Chenies 

 Street, Ciower Street. Mr. Hutchinson points out that 

 lectures will probably be delivered at the .Albert Docks 

 by professors living in the immediate neighbourhood 

 of Harley Street, and be listened to by students living 

 in the neighbourhood of (iower Street ; hence much time 

 will be lost both by teachers and taught, who could 

 obviously come together, for everything except actual 

 bed-side teaching, upon more convenient premises, viz. 

 those of the I'ost-Graduate College. On the other hand 

 it is contended, on the part of the promoters of the Home 

 .Secretary's scheme, that what is required is a school 

 entirely devoted to the study of tropical medicine, where 

 students shall do nothing else, and shall give their whole 

 time to this branch of medicine. It cannot be denied 

 that living in the atmosphere of a subject is greatly 

 conducive to the quick acquisition of a knowledge of it. 

 How this result is brought about is not quite so clear ; 

 it seems to be a kind of intellectual osmosis. .Apparently 

 what the Home Office want is to run their candidates 

 quickly through somewhere where they can quickly 

 yain a good knowledge of tropical medicine, and be 

 then able to materially aid colonisation. They do not 

 want the time of their candidates wasted in going here 

 for lectures, there for clinical cases, and somewhere 

 else for bacteriology. Whether the extra expense 

 involved in concentrating all the requisites for this 

 special education under one roof will be money spent 

 to the greatest advantage from the point of view of 

 general medical education, is perhaps qucstionabU'. The 

 scheme will, however, appeal to the commercial and 

 philanthropic interests involved as business-like, and will 

 probably receive their support. It is to be hoped that 

 neither the local interests of medical cliques on the one 

 hand, nor the colossal dignity of the College of Physicians 

 on the other, will prevent the whole medical profession 

 co-operating to the attainment of a thorough knowledge 

 of tropical medicine by all those who intend to be con- 

 cerned in its practice. 



SOILS FOR ARTIFICIAL CULTURES. 



AN increasing amount of experimental work on the 

 growth of plants is being done by means of cultures 

 in artificial soils. It is quite clear that the success of 

 investigations so conducted must largely depend on 

 the perfect suitability of the soil for the production of a 

 full and normal growth. Little attention is, however, 

 frequently given to this point. It is, in fact, often 

 assumed that a pure quartz sand watered with a nutritive 

 solution supplying phosphates, sulphates and chlorides, 

 of potassium, calcium, magnesium and iron, is a fit and 

 proper soil, and that any deficiency of luxuriance in plants 

 grown in such a medium is due to some special circum- 

 stance unconnected with the general conditions of the 

 experiment. 



Whether some plants are capable of reaching a fair 

 development when placed under the conditions just 

 described is hardly the tiuestion ; the |)oint on which I 

 wish to lay stress is that such a soil is in several respects 

 a most unnatural medium for plant growth, and is thus 

 generally unsuited for purposes of investigation. 



The salts just named are often spoken of as constituting 

 a "full mineral supply," and the conditions described are 

 reckoned as quite suitable for the culture of a leguminous 

 plant, which derives its nitrogen from the atmosphere, if 

 only the organism producing nodules on the roots is also 

 introduced. It is quite true that the silt-- in question, if 

 applied to an ordinary arable soil, woiili.1 furnish an 



NO. 1527, VOL. 59] 



adequate supply of the ash constituents demanded by the 

 plant ; but in this case the form in which they would 

 reach the plant would be entirely different from that which 

 occurs in the case of the artificial soil of quartz sand. 



In the natural soil, containing calcium carbonate, 

 hydrate silicates, and hydrate ferric oxide, all the alkali 

 salts applied as manure are decomposed ; their acids 

 combine with the lime of the soil, and their bases are 

 held in feeble combination on the surface of moist silicates 

 and ferric oxide, from which they are easily extracted by 

 the acid sap of the root hairs. What an immense 

 diflTerence this must make to the plant ! In the first place, 

 there is no hurtful excess of saline matter in the soil. The 

 potash has been precipitated upon the surface of the soil 

 particles, while the acid it was formerly combined with 

 has been carried ofli" united with lime in the drainage 

 water. In the next place, the plant is well provided with 

 bases with which the organic acids which it is constantly 

 producing can combine. This is surely a most important 

 point. What can a plant do that is fed on chlorides and 

 sulphates in a mass of pure quartz? How can it get rid 

 of the acids, and obtain bases to supply its own wants? 

 It must be, at least, a very slow and painful business. In 

 a natural fertile soil, not only are the alkalies, as already 

 mentioned, largely supplied to the plant as bases, but the 

 soil water itself always contains a quantity of calcium 

 carbonate dissolved in carbonic acid. 



That a plant does require this supply of bases is 

 evident from the character of plant ash. The ashes of 

 plant leaf and stem are always of an alkaline character ; 

 those from leguminous plants are highly alkaline, and 

 consist chiefly of carbonates, the residues of the salts of 

 organic acids which have been destroyed on ignition. 



The immense improvement in the luxuriance of an 

 artificial culture in sand which is observed when a nitrate 

 is added to the nutritive salts employed, is not to be 

 entirely attributed to the supply of nitrogen thus given. 

 The nitrate is, in this case, the only salt which can supply 

 the plant with a base, and its addition to the soil thus 

 greatly improves the general conditions of growth. The 

 nitrate acts in this way because the nitric acid is em- 

 ployed in the plant for the production of nitrogenous 

 organic matter, and its base at once becomes available 

 for combination with organic acids. 



For most experiments there is no necessity for employ- 

 ing the favourite mixture of quartz sand and soluble 

 inorganic salts. Any fertile sandy soil may be used as 

 well, and can be as thoroughly steriliseil if sufficient care 

 be taken, but it should not be dried or burnt if its special 

 chemical properties are to be retained. If the nearly 

 complete absence of organic matter is desired, the sand 

 can be taken two feet below the surface. 



If an artificial soil is needed, the quartz sand should in 

 every case be mixed with 25 per cent, of calcium car- 

 bonate. Powdered felspar is an excellent addition to an 

 artificial soil The mixture must also have a sufficient 

 power of holding water ; the sand must, therefore, be fine. 

 If the conditions of the experiment do not forbid it, some 

 humic matter should be supplied. Mr. Mason, who has 

 been very successful with cultures in artificial mixtures, 

 adds I per cent, of moss-litter to his soils. The water in 

 natural soils always contains carbonic acid. This point 

 also must not be forgotten, especially when no addition 

 of humic matter has been made. R. W.XRINGTON. 



NOTES. 

 O.N Monday .It Osborne the (,)uecn held a private investure of 

 the Orders of the Ualh, St. Michael and St. Oeorge, and the 

 Star of India. Sir William Roberls-Au.stcn, K.C.B., and Sir 

 William Thiscllon- Dyer, K.C.M.G., had the honour of knight- 

 hood conferred upon them. Sir Charles Cameron received the 

 decoration of the civil division of the third class of the Order of 

 the Bath. 



