Since positive particles of positive rays from hydrogen have the highest value of e / m, these particles are lighter than positive particles obtained from other gases, so it can be assumed that positive particles from all gases contain protons.
Hence, protons are fundamental particles of all substances like electrons. Proton is fundamental particles in all substances, it is not only known by the study of the properties of positive rays but it is also proved by many other types of phenomena.
Radio activity is prominent among them. E Rutherford discovered that bombarding of alpha particles on nitrogen gas produces oxygen gases and protons are emitted.