59 



experience. Those who have not should go to the "Stores," to a 

 dog-dealer's, etc., and buy a kitten or puppy " over distemper.'* 

 They may be told it is so, but the seller will give no guarantee. 



There are many infectious, contagious or inoculable 

 diseases of birds, but the most disastrous is that due to " invisible, 

 ullravisible or ultra-microscopic microbes" which are, as their names 

 imply, too small to be seen by the most powerful microscope yet 

 devised. They have not up to the present been cultivated in an}' 

 known culture medium. They are so small that they pass 

 through some of the finest mesh bacteriological filters. 



Most of the true contagious, infectious, or inoculable 

 diseases of animals, and probably those of man, are due to this 

 class of micro-organism. To give a few instances of the disease 

 they are known to cause. I may mention spotted tobacco-leaf 

 disease, foot-and-mouth disease, cattle- plague, Cape horse-sick- 

 ness, swine-fever, (which now includes swine-fever proper and 

 swine-plague), canine and feline distemper, fowl-plague, pheasant- 

 plague, bird-plague, rabies, malarial catarrh of sheep, pernicious 

 anaemia of horses, contagious conjunctivitis of cattle, sheep and 

 goats, yellow-fever of man, etc. The contagious pleuro-pneumonia 

 of oxen is due to an almost invisible microbe which passes through 

 filters having a certain degree of porosity, and which has been 

 cultivated in collodion sacs inserted in the peritoneal cavity of 

 the rabbit and external to the animal body, in both liquid and 

 solid media. 



But, as I have said above, birds may die of many in- 

 fectious diseases, the majority of which are due to microbes dis- 

 coverable by the microscope. They include tuberculosis, bird- 

 cholera (a septicaemia), bird-fever (so-called bird-plague), which 

 has been studied by Rieck of Dresden in iSSS, Clarke, Kern of 

 Buda-Pesth in 1895, and Creswell, among others ; colon-bacilli 

 infection, avian diphtheria (not allied to human diphtheria), avian 

 choleraic gastro-enteritis, spirochaetosis, spirillosis, etc. 



There are many other diseases of birds, such as piroplas- 

 mosis, trypanosomiasis, etc., which require to be elucidated. The 

 cause of grouse-disease is not known, but it is very likely due to 

 an " invisible micro-organism." The same may be said of con- 

 tagious epitheliosis, a disease commonly confounded with avian 

 diphtheria. 



