Glass feeding bottle, 1911
The introduction of clear glass feeding bottles in the 1840s began to make feeding a more hygienic process. It was at least possible to see when traces of food had become stuck inside the bottle, which had not been the case with the earlier ceramic ones. A new type of glass bottle, which became popular in the 1870s, contained tubes to improve the flow of the food. However, the tubes were almost impossible to clean properly, and it was not fully understood that sources of infection could be invisible. Those bottles eventually became known as 'killer' bottles due to the number of infant deaths that they were calculated to have caused.
Double-ended bottles like the Allenbury addressed both issues. They improved the flow of food safely, by the use of a rubber valve at one end and a rubber teat at the other. They were also easier to clean because when the valve and teat were removed, the bottle could be washed through under a running tap.