February 19, 1892. j 



SCIENCE. 



105 



possible to verify this phenomenon, nor could this fact serve 

 to establish our proposition; for in his case the substance in 

 question was arsenious acid, while the colors used in dyeing 

 are salts of this acid, generally with a cupric base (Scheele's 

 and Schweinfurth's greens), or sulphids of arsenic (realgar, 

 orpiment). And it is obvious that this circumstance is not 

 irrelevant; for arsenic or arsenious acid may be compatible 

 with the life of certain germs while arseniteof copper may be 

 incompatible, and, indeed, would at first sight appear to be 

 so, if we consider the well-known antiseptic action of the 

 salts of this metal. 



- Hence, in order to prove that tapestries which contain ar- 

 senical colors can become poisonous by reason of the trans- 

 formation of the coloring-matter itself into volatile poisons 

 as a result of the biological activity of the micro-organisms 

 that vegetate in contact with it, it is necessary to prove that 

 these micro organisms can exist with and do transform pre- 

 cisely those colors which are used in tapestries. 



My experiments bring a contribution to this interesting 

 question of hygiene and toxicology. The results obtained 

 allow us to determine not merely whether from solid com- 

 pounds of arsenic and from which of them (arsenious acid, 

 arsenic acid, arsenites, arseniates) it is possible, through the 

 action of microphytes, to develop arseniuretted hydrogen gas 

 or volatile arseno-orgauic products, but also to determine 

 what species are pre-eminently suited to produce this trans- 

 formation. In the first place I prepared some potato pulps 

 containing from 0.05 to 0.1 of arsenious anhydride to 1.000 

 of pulp. These, distributed in several broad Petri capsules, 

 were kept for some days uncovered in a cellar. Soon the 

 growth of moulds and of the common bacteria of the air was 

 very abundant, and at the end of one week a strong smell 

 of garlic began to be perceived, showing that gaseous arseni- 

 cal emanations were taking place. The cultures were then 

 placed in a large damp chamber, from which, by means of 

 an automatic pump, a continuous current of air was drawn, 

 and this was made to bubble up during about two weeks 

 through a solution of nitrate of silver. A strong reduction 

 of this salt, together with the formation, in Marsh's appara- 

 tus, of arsenical rings and spots obtained from the liquid 

 after the elimination of the silver, were the indisputable 

 proofs that the cultures had developed a reducing arsenical 

 gas. 



While this was a positive indication of great value in 

 reaching a conclusion, other arsenical pulps in which also 

 germs of many species had been developed gave no evidence 

 of having undergone a similar decomposition. This dispar- 

 ity of results, if on the 01 ^"nd it justifies the discordant 

 ' "•'^otisators, must, on 



~<^neric 



phere, nutrition, etc., had remaineu ..^ 

 began the work of separating the germs and inc - 

 experiments on pure cultures, of which I will treat in detail 

 in my larger work. Of the germs thus isolated some belong 

 to the moulds, others to the schizomyeetes; among the former 

 I note penicillium glaucum, aspergillum glaucum, and, 

 above all, as greatly preponderating in the mother culture, 

 mucor mucedo. I would also have endeavored to ascertain 

 exactly the species of other moulds and of the other sapro- 

 phytes, if I had found them capable of bringing about the 

 important transformations to which I refer, which was not 

 the case. 



Nevertheless, each of the germs obtained in pure culture 



and others also which are most commonly kept in the labora- 

 ties (B. radiciforme, B. prodigiosum, B. subtile, yellow sar- 

 cina, etc ) were cultivated separately in sterilized potato 

 pulp rendered arsenical by 0.05 grams per 1,000 of arsenic 

 acid. The cultures were kept at the temperature of the sur- 

 rounding air (20°-37° C), and in diffused light. After one 

 month of observation I was able to ascertain that the pro- 

 duction of arsenical gas (indicated by the characteristic gar- 

 lic smell) had taken place only in the cultures of mucor 

 mucedo and (in a far less degree) in that of aspergillum 

 glaucum. It was not perceived in any of the other cultures. 



In view of these facts, special importance attaches to mu- 

 cor mucedo, a mould very widely diffused in our atmosphere 

 and capable of I'educing remarkable quantities of arsenic 

 acid, as I have been able to make sure by strict cliemical re- 

 searches on the abundant cultures carried on in presence of 

 ai'senic anhydride and of alkaline arseniates. 



In another series of experiments, intending to follow out 

 the practical direction that I liad adopted, I inquired whether 

 this activity of the mucor could he extended to those prepa- 

 rations of arsenic which the art of dyeing utilizes in the col- 

 oring of papers and hangings in general. To this end the 

 cultures were carried on in the presence of Scheele's green, 

 Schweinfurth's green, realgar and orpiment. 



Without here dilating on the course of each separate ex- 

 periment and on the method of chemical investigation pur- 

 sued (a thing which I will do in my forthcoming publica- 

 tion) I will sum up my matter in the following corolla- 

 ries : — 



1. Mucor mucedo tolerates remarkable quantities of arsenic 

 not only without injury, but with advantage to its nutrition, 

 for it grows more vigorously. 



2. Many solid compounds of arsenic are, through the bio- 

 logical activity of the fungus that vegetates in contact with 

 them, transformed into gaseous combinations, of which ar- 

 seniuretted hydrogen is certainly one. 



3. This transformation is brought about more or less rap- 

 idly, but is constant and lasting in the case of all the oxygen 

 compounds of arsenic, including arsenite of copper, which is 

 the basis of the green arsenical colors used in dyeing. It 

 does not appear to take place in the case of the sulphids of 

 arsenic (realgar, ofpihient) although the presence of these in 

 the cultures is not at all detrimental. 



4. In given conditions of humidity, temperature and light, 

 arsenical gases may be given off from hangings colored with 

 Scheele's and Schweinfurth's greens, through the vegetation 

 of the mucor (I cannot say yet whether of all the mucorini): 

 hence the danger to those who live in such an atmosphere. 



This statement of mine does not, of course, exclude the 

 possibility that poisoning may be caused through inhaling 

 ^ne dust, as William Forster thinks. But it is evident 

 nly happen as an exception, inasmuch as 

 iition of the production of the fine dust is 

 of dryness of the walls to which the papers 

 we have seen that the poisonous character 

 of arsenica. gings is generally favored by a certain de- 

 gree of humidity and can be suspected from a more or less 

 inlense smell of garlic in atmospheres which answer to the 

 above-mentioned conditions. 



I cannot yet say whether the product of the action of mu- 

 cor mucedo on the oxygen compounds of arsenic is entirely 

 arseniuretted hydrogen. I have reason to think that it is 

 not. By the action of alkalies I have, in fact, constantly 

 succeeded in setting free a volative substance smelling 

 strongly of garlic from the silver solutions employed to oxi- 



