<10-' 



NA TURE 



[February 26, 190^ 



befoie immersion by those who were unacquainted with the 

 motives or circumstances of the experiment. 



" To discover whether a similar change would be produced 

 in the colour of the venous blood in hot air, a dog at 102° was 

 placed in air at 134°. In ten minutes the temperature of the 

 dog was 104^°, that of the air being 130 . In fifteen minutes 

 the dog was 106 , the air 130°. A small quantity of blood was 

 then taken from the jugular vein, the colour of which was 

 sensibly altered, being much lighter than in the natural state. 

 The effect produced by external heat on the colour of the venous 

 blood seems to confirm the following opinion, which was first 

 suggested by my worthy and ingenious friend, Mr. Wilson, of 

 Glasgow. Admitting that the sensible heat of animals depends 

 on the separation of absolute heat from the blood by means of its 

 union with the phlogistic principle in the minute vessels, may 

 there not be a certain temperature at which that fluid is no 

 longer capable of combining with phlogiston, and at which it 

 must of course cease to give off heat ? It was partly with a 

 view to investigate the truth of this opinion that Dr. Crawford 

 was led to make the experiments recited above." 



These views of Dr. Crawford and " his worthy and ingenious 

 friend, Mr. Wilson, 1 of Glasgow," express, about as well as it 

 was possible to express before the chemical discoveries of car- 

 bonic acid and oxygen, the now well-known truth that oxygen 

 carried along with, but not chemically combined with, food in the 

 arteries, combines with the carried food in the capillaries or 

 surrounding tissues in the outlying regions and yields carbonic 

 acid to the returning venous blood, this carbonic acid giving the 

 venous blood its darker colour, and being ultimately rejected 

 from the blood and from the body through the lungs, and 

 carried away in the breath. Crawford's very important dis- 

 covery that the venous blood of a dog which had been kept for 

 some time in a hot-water bath at 112 Fahr. was almost undis- 

 tinguishable from its arterial blood proves that it contained 

 much less than the normal amount of carbonic acid, and that it 

 may even have contained no carbonic acid at all. Chemical 

 analysis of the breath in the circumstances would be most 

 interesting ; and it is to be hoped that this chemical experiment 

 will be tried, not only on dogs, but on men. It seems, indeed, 

 with our present want of experimental knowledge of animal 

 thermodynamics, and with such knowledge as we have of 

 physical thermodynamics, that the breath of an animal kept for 

 a considerable time in a hot-water bath above the natural 

 temperature of its body may be found to contain no carbonic 

 acid at all. But even this would not explain the generation of 

 eold which Dr. Crawford so clearly and pertinaciously pointed 

 out. Very careful experimenting ought to be performed to 

 ascertain whether or not there is 'a surplus of oxygen in the 

 breath ; more oxygen breathed out than taken in. If this is 

 found to be the case, the animal cold would be explained by 

 deoxidation (unburning) of matter within the body. If this 

 matter is wholly or partly water, free hydrogen might be found 

 in the breath ; or the hydrogen of water left by oxygen might 

 be disposed of in the body, in less highly oxygenated compounds 

 than those existing when animal heat is wanted for keeping up 

 the temperature of the body, or when the body is dynamically 

 doing work. 



BACTERIAL TREATMENT OF CRUDE 

 SEWAGE. 



"THE fourth report on the experimental treatment of crude 

 sewage in settling tanks and coke-beds has just been made 

 public by the London County Council.' 2 The work under notice 

 was commenced in April, 1898, at the Barking and Crossness 

 outfall works, where the sewage of the County of London and 

 of certain neighbouring districts is discharged into the lower 

 Thames. 



The plan of experiment was suggested by the chemical 

 adviser to the Council, and has been carried out under his direc- 

 tion and supervision, with the cooperation of the chemists and 

 superintendents at the outfalls. A very small fraction of the 

 sewage only has been thus treated, but in quality it has fairly 



1 Who, no doubt, was Dr. Alex. Wilson, first professor of astronomy in 

 the University of Glasgow (1760-1784) ; best known now for his ingenious 

 •. lews regarding sun-spots. 



- " Bacterial Treatment of Sewage." Fourth Report by Dr Clowes. 

 Published for the County Council by P. S. King and Son, 2, Great Smith 

 Street, Westminster.) 



NO. 1739, VOL. 67] 



represented the immense volume which arrives continuously from 

 the sewer system of the metropolitan area. The results which 

 are summarised in the report may therefore be looked 

 upon as representative, and the conclusions and recommenda- 

 tions which have been founded upon them may be considered 

 to be reasonably applicable to the entire metropolitan sewage 

 discharge. The report gives a general rituvti of the four 

 years' experimental work, which has now led to results of so 

 satisfactory a nature that the tentative treatment has been dis- 

 continued with the view of making a commencement of work 

 on the large scale. ■ 



The early experiments were carried out with crude sewage, 

 which had only been screened from its grosser suspended 

 matters. This was allowed to flow into tanks filled with frag- 

 ments of hard coke of uniform size. As soon as this bed was filled 

 to the surface of the coke, the sewage was allowed to remain at 

 rest for two or three hours and was then drained off from 

 below. After the coke had remained for about five hours with 

 air in the interstices, a second quantity of sewage was allowed to 

 flow in as before. This cycle of processes was repeated for 

 many months, and in some later experiments for more than a 

 year. 



The sewage was clarified by this treatment, but no purification 

 from dissolved organic matter occurred in the early stages with 

 a new bed. After the bed had been at work for about a week, 

 however, it gradually began to effect a marked purification 

 of the sewage from its dissolved putrescible matter. After 

 two or three weeks, the contact of the sewage with the coke 

 effected a removal of from 50 to 60 per cent, of the dissolved 

 putrescible matter. This degree of purification was steadily 

 maintained when the bed had been once "matured,'' and the 

 e (fluent sewage was found to be non-putrescible even when it was 

 maintained at summer-heat (So° F.) in an incubator. Hence 

 the oxidisable organic matter which remained in the effluent 

 was not such as would lead to offence when the effluent was 

 discharged into an ordinary watercourse. 



The treatment of the crude sewage, as judged by 

 chemical criteria, was therefore successful. Dr. Houston, 

 however, stated that, bacteriologically considered, this 

 effluent was not appreciably better than the clear untreated 

 sewage. But this he considered to be unimportant in the 

 case of an effluent which was discharged into the muddy and 

 brackish lower river, the water from which could never be 

 used for drinking purposes. 



A more serious difficulty, however, was soon encountered. 

 It became necessary to ascertain what was the working sewage 

 capacity of the coke-bed, in order to be able to state what area 

 of land would be required to be laid down in coke-beds for the 

 treatment of the whole of the London sewage. On gauging at 

 frequent intervals the sewage capacity of a bed, it was found 

 that the capacity decreased at a uniform and rapid rate, and 

 that after use for about two years the bed would become 

 practically choked and unable to receive its supply of sewage. 



An examination of the coke surfaces showed that a gelatinous 

 growth had formed upon them ; this proved to be bacterial in 

 nature, and necessary for producing the purifying effect. It 

 was found, however, that this growth was impregnated with a 

 certain amount of grit, evidently road detritus, and that woody 

 fibre from the wood pavements and chaff and straw fragments 

 from the horse droppings in the streets were also present in some 

 quantity. It appeared that the gelatinous bacterial growth was- 

 a normal and necessary result and was definite in amount, but 

 that the other matters derived from the street traffic accumulated 

 on the coke and reduced the sewage capacity of the bed at an 

 almost uniform rate. 



Experiments on the preliminary sedimentation of the sewage 

 were made by allowing it to flow through troughs and tanks on 

 its way to the bed, and they proved that the gritty and cellulose 

 matters could be almost completely separated from the sewage 

 before it reached the coke-bed, and that this could be effected 

 withoutallowing the comminuted fecal matter to settle in any 

 large degree. The matter thus separated by subsidence could 

 be dried and in large part consumed in a destructor, the mineral 

 portion being left as a useful clinker. The sedimented sewage 

 was found to undergo satisfactory purification in the coke-bed 

 without diminishing its sewage capacity. 



It was evident that coke-beds must not be allowed to receive 

 mineral detritus from the wear and tear of the roads, and that the 

 cellulose matters derived from the roads were equally objectionable 

 since they were not removed by bacterial action in the coke-bed as 



