An invention is not immediately regarded as incapable of being performed on account of a reasonable degree of difficulty experienced in its performance ("teething troubles", for example).

1st example: The difficulties which could, for example, arise from the fact that an artificial hip joint could be fitted to the human body only by a surgeon of great experience and above-average ability would not prevent manufacturers of orthopaedic devices from deriving complete information from the description with the result that they could reproduce the invention with a view to making an artificial hip joint.

2nd example: A switchable semiconductor which, according to the invention, is used for switching electrical circuits on and off without using contacts, thereby making for smoother operation, suffers from teething troubles in that a residual current continues to flow in the circuit when switched off. However, this residual current adversely affects the use of the electrical switch in certain fields only, and can otherwise be reduced to negligible proportions by routine further development of the semiconductor.