84 Ihr-lt'tf pniij ill V'lvtoiiii. 



Sacbrood. 



(Jn pas^e 3 of the pamphlet referred to, Dr. AVliite, conceruiug the 



syiiiploiiis, says : — 



" The strength of a colony m which sacbrood is present is frequently 

 not notieeablj' diminished. When the brood is badly infested, how- 

 ever, the colony naturally becomes appreciably weakened thereby. 

 The brood dies after the time of capping. The dead larvaj are there- 

 fore almost always found extended lengthwise in the cell and lying 

 vv'ith the dorsal side against the lower wall. It is not unusual to find 

 many larva' dead of this disease in uncapped cells. Such brood, 

 however, had been uncapped by the bees after it died. In this disease 

 tlie cappings are frequently punctured l)y the bees. Occasionally a 

 eapping has a hole through it, indicating that the capping itself had 

 never been completed. A larva dead of this disease loses its normal 

 colour and assumes at first a slightly yellowish tint. ' Brown ' is the 

 most characteristic appearance assumed by the larva during its decay. 

 Various shades arc observed. The term ' gray ' might sometimes 

 appropriately be used to designate it. The form of the larva dead 

 of this disease changes much less than it does in foul-brood. The 

 liody wall is not easily broken, as a rule. On this account often the 

 entire larva can be removed from the cell intact. The content of this 

 sac-like larva is more or less watery. The head end is usually turned 

 markedly upward. The dried larva or scale is easily removed from 

 the lower side wall. There is practicall}' no odour to the lirood 

 combs. 



" The Infectious Nature and Cause of Sacbrood. 



" In the study of samples of this disease received directly from bee- 

 keepers no micro-organisms have been found, either culturally or 

 microscopically, to which the cause of the disease can be attributed. 

 This fact, together with the fact that the disease often disappears 

 without an}^ great loss to the colony, would tend to indicate that the 

 disease is not infectious. The experimental evidence which I have 

 obtained proves, however, that the disease is infectious. 



" Experimental "Work with Sacbrood. 



" Evidence has been obtained by me that sacbrood can be trans- 

 mitted from diseased to healthy brood. Three healthy colonies were 

 inoculated, each with diseased material from a different locality, and 

 in each of these three experimental colonies the disease was pro- 

 duced. These results indicated at once that sacbrood is an infectious 

 disease. The microscopical and cultural study of the infected and 

 dead brood in these experimental colonies, as in the case of the diseased 

 brood in samples direct from the apiai\y, failed to show any organism 

 to which the cause of the disease could be attributed. 



" This led naturally to a study of the condition to determine whether 

 or ]iot the virus of the disease was so small that it had not been seen. 

 To obtain evidence on this point material containing the virus was 

 filtered using an earthenware filter. The three colonies in which 

 the disease had been produced experimentally furnished the disease 



