Dracula - Chapter X HELP

I am trying to make sense of a passage and would appreciate some help understanding.
In the third paragraph into Dr. Seward's Diary, Van Helsing begins to talk about sowing corn to shed light on Lucy's situation... what does he mean?

This is a link to the chapter and text I am referring to: http://www.online-literature.com/stoker/dracula/10/

I am understanding this analogy as a "don't count your chickens before they're hatched" type of explanation. Van Helsing doesn't want to say that Lucy will be alright ("will make a good crop when the time comes") unless he can know this for sure through further examination.

Am I understanding this passage correctly?? Help.

Van Helsing is advocating patience - it would be dangerous to attempt to interfere too soon in Lucy's condition. He knows what is ailing her but is wary of making any rash moves.
In the same way that a farmer must wait for the first ear of corn to emerge from the stem before testing the quality of the new seed so Van Helsing knows he will have to wait for Lucy's illness to reach a climax before he can be sure of the best way to proceed.

H

H - Thank you for the input. :)