258 PROCEEDINGS OF SOCIETIES. 



under 500,000 ; aud tlie want of knowledge, even among very intel- 

 ligent persons, concerning the practical requirements for limiting the 

 spread of contagious diseases is deplorable, so that in epidemics the 

 scourge is sometimes fostered and spread by the very persons in charge 

 of the sick, sometimes by the patients themselves being allowed to mix 

 with the healthy and distribute far and wide the germs of disease. 

 Heads of families are not always aware that a child who has completely 

 recovered from scarlet fever, and is in fact well, may communicate it 

 to half the children he comes in contact with, unless he be placed in 

 quarantine for three months at least, by which time there is reason 

 to believe that all active contagious particles will have become obli- 

 terated. 



This germ theory of disease has lately been brought into consider- 

 able notice in consequence of Professor Tyndall's lectures at the Eoyal 

 Institution on dust and haze, in which he sought to prove that the 

 particles floating therein are germs of animal and vegetable, probably 

 the seeds of infectious disease. Professor Beale, however, has, by the 

 aid of a ^L inch objective, discarded the vegetable germ theory, and 

 propounded a bioj)lasm or minute morsel of germinal matter, possess- 

 ing a sej)arate vitality, distinct from the organism into which it may 

 become absorbed, and developing within the fluids of the containing 

 organism. 



Passing on now from these subjects to one of more domestic interest, 

 the detection of adiilteration in our foods, drinks, and drugs, opens up 

 to us all a ready and useful application of the microscope. Until some 

 legislative act shall provide public analysts and inspectors, so long 

 will adulteration greatly prevail. It is exceedingly difficult, if not 

 impossible, to procure wholesome, unadulterated food : and although 

 an Act of Parliament has existed since 1860, not a single conviction 

 has been obtained under it in the metropolis. 



The adulteration of tea gives us a very good example of the extent 

 to which what is called sophistication is carried on. Tea is doubly 

 dealt with in the way of fraud, for it receives a first instalment at 

 the hands of the producers, and a second at the hands of the dispensers 

 at home ; although the latter may receive the credit of doing nothing 

 very venomous, but chiefly by way of diluting a good with an inferior 

 article, and colouring uj) a common caper into fine gunpowder by refac- 

 ing the tea with chalk and prussian blue. The adulterations practised 

 by the exporters in China are in the glazing, the use of many delete- 

 rious mineral substances, such as plumbago (carburet of iron), chrome 

 yellow (chromate of lead), Scheele's green (arsenite of copper), in 

 drying up the leaves of other plants with the tea, such as those of the 

 willow, the beech, the elm, the plane, the sloe, &c., and in redrying 

 the leaves of tea that have already passed through the pot. But the most 

 startling, because the newest, is what is called the Maloo mixture, 

 from its resemblance to the tan with which the Maloo race-course is 

 strewed. It is extensively employed for mixing with tea, or even sold 

 as tea itself; and it is said that 30,000Z. worth of this wretched com- 

 pound was recently on its way to this country. The Chinese collect 

 all the used-up tea-leaves they can get, and keep them in heaps 



