Nosodes are homeopathic remedies prepared from diseased tissues, secretions, or excretions. The correct matching of the nosodes in List I with their sources in List II is as follows:
\begin{itemize}
\item Proteus (A) is a nosode prepared from bowel nodes (II), specifically from the Proteus bacteria isolated from them.
\item Pyrogenium (B) is a nosode prepared from the decomposition of meat of beef (IV) or sometimes from septic pus.
\item Nectrianinum (C) is a nosode prepared from a fungus, \( \textit{Nectria ditissima} \), which causes cancer of trees (I) (canker).
\item Diphtherinum (D) is a nosode prepared from the disease product of human beings (III), specifically from the Klebs-Loeffler bacillus or the diphtheritic membrane.
\end{itemize}
Therefore, the correct combination is (A)-(II), (B)-(IV), (C)-(I), (D)-(III).